Antibodies against aflatoxin B1 have been raised in rabbits using aflatoxin B1-histone H1 conjugates as immunogen. Aflatoxin B1 was coupled to histone H1 via the ultimate carcinogen aflatoxin B1-2, 3-epoxide. The antibodies are specific for aflatoxin B1. The average number of binding sites on the antibody molecules for aflatoxin B1 as obtained from Scatchard plot analysis of the binding data is 1.94 with < F degree = -6.19 Kcal/mol, while the average association constant for the binding is 34.5 x 10(3) M-1. Male wistar rats after immunization with aflatoxin B1-histone H1 showed lower mortality and reduction of acute toxic effects in the liver when challenged with a single dose of aflatoxin B1. The antibodies may be useful in immunoprophylaxis against aflatoxicosis.