The present study examined biochemical storage lesions in 58 buffy coats (BCs) intended as the raw material for platelet concentrates. The work was conducted in three series; the aims were to investigate: (a) the storage quality of BCs obtained from the routine production (series I), (b) whether improvement in platelet quality could be achieved by continuous agitation during storage (series II), and (c) whether macroscopic aggregate formation indicates platelet damage (series III). Series I and II consisted of 20 BCs each. Series III compared ten BCs with visible clumping with eight BCs not demonstrating macroscopic aggregates. In series I and II platelet counts and platelet factor 4 (PF4) release were determined after 1, 3, 5, and 24 h; lactate dehydrogenase (LDH) extracellular activity was measured after 1 and 24 h. In addition, in series I elastase concentrations were analyzed after 3, 5, and 24 h. Finally, in series III extracellular beta-thromboglobulin (beta-TG) levels were determined after 18-24 h. Low platelet counts, most likely reflecting the presence of aggregate formation, were found in 20% of the BCs (series I); in this series a total of 25% demonstrated increasing platelet counts, together with elevated PF4 and elastase, over the study period. Significant biochemical storage lesions were found after 5 and 24 h of storage. The study also demonstrated that continuous agitation during storage does not improve platelet quality (series II) and that BCs demonstrating visible clumping (series III) had augmented levels of extracellular beta-TG (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)