The Friend helper leukemia virus (F-MuLV) induces in mice leukemias of the erythroid, lymphoid, and myeloblastic lineages. Erythroleukemic cell DNAs were examined for genetic alterations at loci described as common proviral integration regions in MuLV-induced myeloid or lymphoid leukemias or in Friend complex-induced erythroleukemias. No alteration of the Fim-1, Fim-2, Fim-3, pvt-1, and Spi-1 loci were detected in 17 erythroleukemias, p53 gene rearrangement was observed in 6 (30%) erythroleukemias and was always associated with a loss of the germ line allele. Interestingly, genetic alterations were also detected at two loci, c-myc and Pim-1, previously described as common provirus integration regions in T lymphoid leukemias. Rearrangements of these two genes were often associated with p53 gene alteration within the same tumor.