Abstract: The radiation-induced agouti allele a1 was found to be recessive to the alleles a and a4H (which resembles ae ). It was also found to be lethal when homozygous and when in combination with the dominant yellow allele Ay . The ethylnitrosourea-induced allele a16H was lethal when homozygous, and when heterozygous with a showed a phenotype like that of ax , with black back and lighter belly. Like ax , it was not lethal in combination with ay or a 1 . The allele a1 is believed to be the first reported recessive allele which is lethal in combination with Ay , and may be useful in elucidating the complexity of the agouti locus.