We have constructed and analysed somatic cell hybrids from cell lines containing balanced reciprocal translocations involving chromosome 19 and providing two new breakpoints on 19q. These and other hybrids have been tested with a series of markers from 19q to enhance the existing map. Several new cloned DNA sequences that map to 19q13.3-19qter are reported; the locus D19Z1 has been analysed by CHEF gel electrophoresis.