The present study compares some properties of platelet concentrates, i.e. their ability to transmit light and the degree of platelet lysis and the deterioration of the platelet membrane glycoprotein Ib (GPIb). Extracellular levels of glycocalicin and lactate dehydrogenase (LDH) served as indicators for the proteolytic cleavage of GPIb and platelet lysis, respectively. The light transmission of 16 platelet apheresis concentrates was monitored continuously during storage using a specially designed apparatus. Determination of platelet counts and extracellular glycocalicin levels was carried out on day 1. In addition, after 7 days of storage extracellular concentrations of LDH and glycocalicin were determined. After 7 days highly significant correlations were found both when comparing light transmission changes and extracellular glycocalicin levels (r = 0.78; p < 0.001) and when comparing light transmission changes and extracellular concentrations of LDH (r = 0.83; p < 0.001).