A human plasma cell line designated ARH-77 has been established and propagated in culture for the past 2 years. The cells exhibited morphological characteristics of plasma cells under light and electron microscopic examination. An average of 40% cells are positive for immunoglobulin G by direct immunofluorescence, while an immunoglobulin G-specific radioimmunoassay reveals the production of 1.21 X 10(4) ng/10(6) plasma cells. The karyotype is aneuploid with a a modal chromosome number of 45 to 46 and no marker chromosome. Growth kinetics characteristics are: doubling time, 110.4 hr; generation time, 56.4 hr; G1 + G2-phase transit time, 45.5 hr; S-phase transit time, 10.9 hr; growth fraction, 74%; mitotic index, 1.5%; labeling index, 14.3%; and cell loss, 31.0%. Some of the growth kinetics characteristics were markedly similar to the properties displayed in vivo by plasma cells of patients with multiple myeloma and suggest that the cell line might be a useful in vitro model for the study of human myeloma.