An up-dated survey of the information pertaining to the role of genetic factors in susceptibility to multiple myeloma is attempted. Our own results include the HLA-A, B, and C types in 68 patients, the G1m and Km allotypes in 86 patients, and the frequencies of ABO blood groups in 126 patients with multiple myeloma. The allotype G1m(x) was significantly (p less than 0.05) more frequent in the patient group. Since the results in the literature on a possible HLA association have been inconsistent, all relevant available data were combined for an assessment of 379 patients versus 5041 controls. In this comparatively large patient group, the previously reported increase of HLA-4c (HLA-B5 + B18 + Bw35) complex could be confirmed and identified as a weak (RR = 1.7) but significant (p less than 0.05) association of susceptibility to multiple myeloma with HLA-B5. Evaluation of G1m allotypes in the combined sample of 258 patients and 4550 controls and Km in 179 and 2457, respectively yielded no significant differences.