The aim of study was to evaluate the function of modified platelet additive solution (PAS-IIIM) with trehalose as a substitute of plasma for the storage of platelet concentrates at low temperature (10 degrees C). Apheresis platelets from 6 donors were divided and added with different media (group A: 100% plasma; group B: 70% PAS-IIIM/30% plasma; group C: 100% plasma/trehalose). Groups A, B, C were stored at 10 degrees C, 22 degrees C and -85 degrees C separately. In addition, group D (platelet concentrates stored with 100% plasma at 4 degrees C) was set up as control group for scan electronmicroscopy. The samples of each platelets were collected on day 0, 1, 5, 7 and 9 after storage respectively, while samples of platelets stored at -85 degrees C (group C) were collected on day 20 after storage. CD62p, hypotonic shock response (HSR), platelet aggregation, lactic dehydrogenase (LDH) and morphology of platelets were evaluated. The results showed that the expressions of CD62p in groups A and B increased in a time-dependent manner, but HSR and platelet aggregations decreased. The expression of CD62p, LDH release, and platelet aggregation in group A were significant higher than that in group B (p < 0.05). HSR in group A was significant lower than that in group B (p < 0.05). LDH release was significant high in samples of group C and the expression of CD62p was lower than that in other two groups (p < 0.05). It is concluded that the protective effects of 70% PAS-IIIM/30% plasma (10 degrees C) and plasma platelets (22 degrees C) on morphology of platelets are similar, but better than those of plasma platelets (4 degrees C) and plasma/trehalose (-85 degrees C). In short, PAS-IIIM serves as a good substitute of plasma for platelet storage, and protects the chilled platelets.