Rehydrated, mature, undamaged seed of 502 peanut (Arachis hypogaea L.) genotypes were scarified, inoculated with an aflatoxigenic strain of Aspergillus flavus Link, and tested for aflatoxin B₁ production after incubation at 25 C for 10 days. All genotypes supported production of aflatoxin B₁ but significant genotypic differences in levels of aflatoxin B₁ production were found. Genotypes U 4–7–5 and VRR 245 supported the lowest levels of aflatoxin B₁ (< 10 μg/g seed), whereas the commonly grown Indian cultivar TMV 2 supported production of aflatoxin B₁ at levels of over 150 μg/g seed. Eight genotypes with low, moderate or high capacity to support aflatoxin B₁ production were further tested using seed from one rainy season crop, and two irrigated postrainy season crops. Genotypic differences in levels of aflatoxin B₁ production were consistent over seasons. Production levels were slightly lower in seed from the rainy season crop than in seed from the two postrainy season crops.