Three hundred fifteen radiation hybrids (RH) were isolated using a monochromosomal cell hybrid containing chromosome 16 only. A panel of 18 RH, which showed breakpoints among four markers (3.15, 26.6, 3'HVR, and 5'HVR) mapping in the distal portion of 16p, were selected and characterized for the retention of nine additional DNA sequences already localized in this region, and for one centromeric sequence. One or more breakpoints were identified in nine of the 12 intervals defined by the 13 single-copy sequences used. This panel of RH represents a tool for the construction of a detailed physical map of the distal part of 16p and for cloning sequences located in the proximity of disease genes. Three inter-Alu DNA sequences, amplified from one of these RH containing the autosomal dominant polycystic kidney disease (PKD1) gene, were cloned and mapped in the panel. Sequencing of the ends of one of three clones showed a (CAAA)n repeat, which revealed a two-allele polymorphism.