We have assembled a panel of monochromosomal somatic cell hybrids for use in gene mapping. DNA from each individual hybrid was used as a probe on normal human metaphases to identify the human chromosome and any fragments by reverse painting. To test the efficiency of the panel PCR amplification of DNA from the monochromosomal somatic cell hybrid panel was used in combination with human specific oligonucleotide primers to assign α‐catenin (CTNNA1) and p21/WAFl to chromosomes 5 and 6 respectively. These genes were localized further using hybrids containing specific translocations to 5qll‐qter and 6p21 respectively. We also developed primers to enable us to assign 17 ESTs sequenced by the HGMP Resource Centre. The hybrid panel was developed with support of the UK HGMP and the DNA is available to all registered users.