The CEPH consortium map of chromosome 15q is presented. The map contains 41 loci defined by genotypes generated from CEPH family DNAs with 45 different probe and restriction enzyme combinations contributed by 10 laboratories. A total of 29 loci have been placed on the map with likelihood support of at least 1000:1. The map extends from 15q13 to 15q25-qter. Multipoint linkage analyses provided estimates that the male, female, and sex-averaged maps extend for 127, 190, and 158 cM, respectively. The largest interval is 21 cM and is between D15S37 and D15S74. The on-average locus spacing is 5.6 cM and the mean genetic distance between the 21 uniquely placed loci is 8 cM.