A restriction fragment length polymorphism (RFLP) at the human FGR gene, a member of the src family of protooncogenes, has been identified and used to locate FGR on the genetic linkage map of human chromosome 1p. Single-copy sequences subcloned from a cosmid containing the human FGR gene were used to screen a panel of genomic DNAs for RFLPs. One plasmid, designated pB8, detected a high-frequency EcoRI RFLP (allele frequencies, 0.57/0.43). Analysis of a panel of somatic cell hybrids demonstrated that pB8 maps to the region 1p31-pter. Genetic linkage analysis of the 40 families provided by the Centre d'Etude du Polymorphisme Humain (CEPH) showed that FGR maps to a location 3.1 cM from the Rh blood group locus (RH), and falls in the 17.5-cM gap between alpha-fucosidase (FUCA1) and D1S57. The relative gene order of RH and FGR could not be determined unequivocally, but the most favored gene order was 1pter-PND-ALPL-FUCA1-FGR-RH-D1S57-MYCL.