Summary Thirty-seven bone marrow aspirates of human γ and β2A myelomas were smeared and labelled by fluorescent antibodies against γ and β2A globulin. Never were all the observed plasma cells reactive with fluorescent antibodies, and in half of the cases, no fixation by any plasma cell was noted. Plasma cells of different types were fluorescent, most of them having a granular structure. They were found to fix fluorescent antibodies against γ globulin or β2A globulin, but never both.