Circulating immune complexes (cic) were determined by means of the immunoenzymatic method in a group of 16 adults with immune thrombocytopenic purpura (ITP) before and after splenectomy. The recurrence of immune thrombocytopenic purpura after splenectomy was observed in 9 patients, in 6 out of them there co-existed non-specific inflammatory process and cic were present in the serum. In 7 patients in whom the number of thrombocytes after splenectomy was normal, no circulating immune complexes were found. A significant decrease in the medium level of IgM after splenectomy should be attributed rather to splenectomy than to the consuming of IgM in the formation of circulating complexes. The role of circulating complexes in the pathogenesis of ITP in adults still remains not fully solved, but the authors' experience suggests that non-specific inflammatory processes may lead to their appearance.