A study has been undertaken of more than 100 people located on the north coast of the Papua New Guinea mainland, to determine the frequency of the HLA antigens, at the HLA-A, HLA-B and HLA-DR loci in leprosy patients and unaffected family members. Leprosy type had been clinically diagnosed as lepromatous, borderline lepromatous or tuberculoid. To overcome inherent problems of the remoteness of the study population, the lymphocyte typing has been carried out on 3 types of cell preparations. This includes the use of continuous cell lines, derived by Epstein Barr virus transformation of the collected cells and fresh and frozen preparations of B and T lymphocytes. The investigation of an HLA association with leprosy may provide insight into a genetic susceptibility to the disease, as well as the demonstration of the HLA-DR antigen distribution, in the population living in the coastal regions of Papua New Guinea. To explore the mode of transmission of the disease, approximately 20 families have been phenotyped for 12HLA-A, 20HLA-B and 7HLA-DR antigen specificities.