The physiological role of fibronectin (FN) on the human plasma cells were examined using three PC cell lines, FR4ds, OPM1 and OPM1ds. FR4ds was reactive with anti-VLA-alpha 4 and anti-alpha 5. In contrast, OPM1 and OPM1ds were not reactive with anti-VLA-alpha 5. FN induced spreading in FR4ds and OPM1ds. Albumin blocked these spreadings. FR4ds with mature plasma cell phenotype of alpha 4+ and alpha 5+ was more sensitive for FN than OPM1 and OPM1ds with immature phenotype of alpha 4+ and alpha 5-. Spreading cells proliferated more than floating cells. All these cell lines showed chemotaxis toward FN. alpha 5+ FR4ds was more sensitive for FN than OPM1 and OPM1ds with alpha 5- phenotype. These new abilities of PC of spreading and chemotaxis we found are summarized to be an affinity to organs. It is likely that alpha 4+ and alpha 5- PC with low affinity to organs are stored in peripheral blood as a result. We examined the chemotaxtic activity of myeloma cells in bone marrow and these in pleural effusions in a patient with multiple myeloma. These cells in pleural effusions showed more chemotaxic activity than these in bone marrow. FN induced growth, production of Ig, and motility of PC, which resulted in the augmentation of humoral immunity.