Incorporation of [32P]-orthophosphate into plasma phospholipids was investigated in 11 patients with polycythemia vera. The specific activity of phospholipid radioactive precursors (TCA-extract) was maximal 1 hour after the delivery of radioactive phosphorus and dropped to less than 20 per cent of maximal value after 24 hours. The peak of total phospholipid specific activity was observed 48 hours after the administration of [32P]-orthophosphate in 10 patients, and after 24 hours in one, and decreases regularly afterward. The half-life of the lipid-bound phosphorus in the plasma of investigated patients, determined during the decrease of their specific activity was 252+/-60 hours. Concentration of total plasma phospholipids and the pattern of individual phospholipid found in patients with polycythemia vera were similar to those reported for normal individuals. The rate of incorporation of the labeled phosphorus into phosphatidylethanolamine and phosphatidic acid was much more rapid than into lysophosphatidylcholine, sphingomyelin, or phosphatidylcholine.