A complete overlapping clone map of a 1.7-Mb region from DBH to D9S67 that includes the TSC1 candidate region has been constructed. The map includes YAC and cosmid clones, contains STS approximately every 50 kb on average, and establishes the order of five previously unordered loci. The overall physical length of this segment of chromosome 9q34 (1.7 Mb) is significantly less than expected compared to its estimated genetic length (approximately 10 cM). Consequently, the physical length of the TSC1 candidate region is substantially less than predicted by a genetic distance of approximately 2 cM.