In radiation hybrid mapping, chromosomes in human-rodent hybrid cells are fragmented by X-rays and fragments rescued by fusion of the donor cell to a recipient rodent cell. The co-retention frequencies of markers in 100-200 hybrids are used to map individual chromosomes, but mapping the whole genome in this way is impractical. We have reverted to the original protocols of Goss and Harris and have produced a panel of 44 hybrids using irradiated human fibroblasts as donors. This panel has been used to make a map of human chromosome 14 containing 40 ordered markers. The map integrates previously published maps and localizes nine new markers. We suggest that the construction of a high resolution map of the whole human genome is feasible with a single panel of 100-200 hybrids.