A strategy for the analysis of yeast artificial chromosome (YAC) clones that relies on polymerase chain reaction (PCR) amplification of small restriction fragments from isolated YACs following adapter ligation was developed. Using this method, termed YACadapt, we have amplified several YACs from a human Xq24-qter library and have used the PCR products for physical mapping by somatic cell hybrid deletion analysis and fluorescent in situ hybridization. One YAC, RS46, was mapped to band Xq27.3, near the fragile X mutation. The PCR product is an excellent renewable source of YAC DNA for analyses involving hybridization of YAC inserts to a variety of DNA/RNA sources.