Polymorphic variation of the c-raf-1 proto-oncogene is reported here for the first time. In a study of 21 individuals, including 17 with non-Hodgkin's lymphoma and three healthy controls, we have identified three c-raf-1 alleles. One variant allele was observed in both a mother and her son, both of whom had lymphoma, but in no other case. The other variant allele was observed in two patients with lymphoma and in a healthy control.