For the purpose of studying immunogenetic factors related to disease susceptibility to systemic lupus erythematosus (SLE), HLA-A, B and DR typing was performed by the standard lymphocyte microcytotoxicity test using 247 typing antisera in 34 Japanese patients with SLE and 51 healthy individuals.The results obtained were as follows: 1) SLE patients with proteinuria had the association with HLA-BW 35 (phenotype frequency 50.0%, Relative Risk=7.5, corrected P<0.10), compared with normal control (11.8%). SLE patients without proteinuria had the association with HLA-BW 55 (phenotype frequency 35.0%, RR=8.6, Pc<0.10), compared with normal control (5.9%).2) Patients with SLE had the strong association with HLA-DRW 9 (phenotype frequency 52.9%, RR=4.6, Pc<0.025), compared with normal control (19.6%).3) All of the peripheral blood lymphocytes obtained from 10 patients with SLE who had anti-RNP antibody reacted with MT 3, which was one of the B-cell alloantisera including three antibodies against HLA-DR 4, DR 7 and DRW 9.4) The linkage disequilibrium between HLA-BW 61 and HLA-DRW 9 was seen in the patients with SLE.