Freund's Adjuvant is one of the most commonly used adjuvants in research. It is used as a water-in-oil emulsion. It is prepared from non-metabolizable oils (paraffin oil and mannide monooleate). If it also contains killed Mycobacterium tuberculosis it is known as Complete Freund's Adjuvant. Without the bacteria it is Incomplete Freund's Adjuvant. First developed by Jules Freund in the 1940's, Freund's Adjuvant is designed to provide continuous release of antigens necessary for stimulating a strong, persistent immune response1,2,3 The main disadvantage of Freund's Adjuvant is that it can cause granulomas, inflammation at the inoculation site and lesions. The mycobacteria in Complete Freund's attracts macrophages and other cells to the injection site which enhances the immune response. For this reason, the Complete Freund's Adjuvant is used for the initial injections. To minimize side-effects, Incomplete Freund's Adjuvant is used for the boosts.