We examined allelic loss in colon tumors induced by 1,2-dimethylhydrazine (DMH) in F1 hybrid mice, using sequence-tagged microsatellite site (STMS) primers derived from the chromosomal region closely linked to the p53 locus. Polymerase chain reaction--single-strand conformation polymorphism (PCR-SSCP) analysis of 155 colonic tumors with two STMS markers revealed that no genetic alterations had occurred in these tumors, except for one case where one of the markers detected an increase of one CA repeat unit in one allele. No allelic loss at the loci closely linked to the p53 locus strongly suggests that allelic loss at the p53 locus is not involved in DMH-induced colon carcinogenesis in mice.