Our standard protocols use Freunds Complete followed by Freunds Incomplete. In the absence of other information, this is probably what you should use too as it is the most highly documented and most often used system in the literature. Listed below are some of the other currently available options.

• Ribi Adjuvant System (RAS) - Ribi markets a wide variety of immunologic products. The primary product marketed as an alternative to Freund's complete adjuvant is a oil-in-water emulsion containing detoxified endotoxin (MPL) and mycobacterial cell wall components (TDW, CWS) in 2% squalene. It is as convenient to use as Freund's complete adjuvant (or more so because of its lower viscosity) and it has very low toxicity, having been used in humans. In some circumstances, especially in mice, it compares well with Freund's complete adjuvant. Preparation of the adjuvant-antigen emulsion in a tissue grinder with a teflon pestle (Potter-Elvehjem type) is encouraged for optimal results but it is not essential. No longer being produced.  Limited quantities are available from: Sigma M6536
• TiterMax - A product marketed specifically as a replacement for Freund's complete adjuvant, TiterMax is a stable, metabolizable water-in-oil adjuvant, a single injection of which the manufacturer has shown to induce antibody titers greater than 2 injections of Freund's (Freund's complete adjuvant followed by Freund's incomplete adjuvant). Available from: CytRx Corporation 150 Technology Parkway Technology Park/Atlanta Norcross, Georgia 30092  (800)-345-2987
• Syntex Adjuvant Formulation (SAF)³ - Has been developed as an alternative to Freund's complete adjuvant. It is a performed oil-in-water emulsion stabilized by Tween 80 and pluronic polyoxyethlene/polyoxypropylene block copolymer L121. SAF activates complement by the alternate pathway and is said to bias the humoral immune response to IgG2a in the mouse. Like other oil-in-water adjuvants, it works better with proteins that have some hydrophobic aspect to promote their adherence to oil droplets. Available from Chiron Corporation, Emeryville, California.
• Freund's Incomplete Adjuvant (FIA) - the most inflammatory component of FCA, killed mycobacteria, is not included in FIA. FIA is routinely used for boosting immunizations subsequent to FCA. It can also be used for the initial immunization, particularly when a strong antigen is used or moderate antibody levels are sufficient. As with FCA, efficacy is dependent upon vigorous mixing of the adjuvant and antigen until a stable emulsion has formed. Available from: Numerous research product companies.
• ALUM - aluminum hydroxide; Al(OH)3. Aluminum hydroxide is a widely used adjuvant, especially in commercial products such as vaccines. It is very well suited for strong antigens. Many sources of aluminum hydroxide are available. Commercially available as Alhydrogel, Accurate Chemical & Scientific Co, Westbury, New York.
• SuperCarrier - this and some similar products are convenient kits for coupling haptens, such as peptides and small proteins, to larger carrier molecules to enhance immunogenicity. The coupled proteins can be combined with other adjuvants. Syntex Research 3401 Hillview Ave. P.O. Box 10850 Palo Alto, CA 94303
• Elvax 40W^1,2 - this is an ethylene-vinyl acetate copolymer. While the production process is somewhat involved, the resulting immune response can surpass that induced by Freund's complete adjuvant. Sold in 25 gram amounts, however small gratis amounts are available. Available from: DuPont Chemical Co. Wilmington, DE (800)-628-6208; (request Elvax customer representative)
• L-tyrosine - a co-precipitate of the amino acid and antigen has been shown to have excellent adjuvant properties, even surpassing Freund's complete adjuvant in some circumstances. While the co-precipitation procedure is not difficult, it requires some manipulation. The cost is negligible. Available from numerous chemical companies.
• Montanide - a manide-oleate compound that has been shown to produce antibody levels equivalent to Freund's complete adjuvant. Small aliquots are available upon request from the producer. Available from: ISA Seppic Fairfield, NJ
• AdjuPrime - this is a carbohydrate polymer marketed as an alternative to Freund's complete adjuvant. Independent studies comparing its efficacy to other adjuvants do not appear to be available. The carbohydrate is thought to create both a "depot" effect and an enhancement of the interaction between the antigen and antigen-presenting cells.
• Nitrocellulose-absorbed protein⁸- Nitrocellulose-absorbed protein will give a desirable slow release of antigen over a period of 2 weeks to 2 months. The nitrocellulose is inert and causes minimal inflammatory response.
• Gerbu adjuvant - This is an aqueous phase adjuvant that does not have a depot effect. It therefore requires frequent boosting to achieve a high-titer response, but produces minimal inflammatory response. Gerbu adjuvant is available from C-C Biotech, Poway, California.
• Immune-stimulating complexes (ISCOMS) - ISCOMS are Ag-modified saponin/cholesterol micelles that form stable cage-like structures. ISCOM-associated antigen molecules do not form a depot site but are transported to the draining lymph nodes. Quantities of antigen as low as 1 ug have elicited a significant immune response. ISCOMS can be successfully prepared in the laboratory⁹.

References:

1-Niemi SM, et al. Evaluation of ethylene-vinyl acetate copolymer as a noninflammatory alternative to Freund's Complete adjuvant in rabbits. Lab Anim Science 35:609-612, 1985.
2-Silberstein FB, et al. Elvax 40P implants: sustained, local release of bioreactive molecules influencing mammary ductal development. Developmental Bio 93:272-278, 1982.
3-Allison AC, et al. An adjuvant formulation that selectively elicits the formation of antibodies of protective isotypes and cell-mediated immunity. J Immuno Methods 95:157-158, 1986.
4-Rubach JA. Molecularly engineered microbial immunostimulators; In: Technological Advances in Vaccine Development, Alan R. Liss, Inc. 1988; 433-454.
5-Johnston BA, Eisen H, Fry D. An evaluation of several adjuvant emulsion regimens for the production of polyclonal antisera in rabbits. Lab Anim Sci 41:15-21, 1991.
6-Amyx HL. Control of animal pain and distress in antibody production and infectious disease studies. J Am Vet Med Assoc 191:1287-89, 1987.
7-Broderson JR. A retrospective review of lesions associated with the use of Freund's adjuvant. Lab. Anim. Sci. 39:400-405, 1989.
8-Nilsson BO, Larsson A. Inert carriers for immunization. Res. Immunol. 143:553-557, 1992.
9-Coligan LG et al. eds. Current Protocols in Immunology, New York: John Wiley & Sons, 1995.