Abstract: The aim of this study was to analyze the in vitro glyation of human placental collagen (type IV) and to test the effect of glycation on its platelet aggregation activity. After isolation of collagen IV from a normal human placenta, it was glycated using different glucose concentration and different time of incubation. Glycation was measured using thiobarbituric acid colorimetric reaction. Using a turbidimetric method effect of glycated collagen on platelet aggregation was studied and compared with those of non-glycated collagen. The data obtained from this study indicated that collagen underwent in vitro glycation reaction and the level of glycation was dependent on glucose concentration and time of treatment with glucose (p<0.01). Glycated collagen increased platelet aggregation compared with native collagen (p<0.01). These results suggest that hyper-aggregability of platelet in interaction with glycated collagen can be the result of modification in collagen structure. The observed carbohydrate-induced modification apparently have a major impact on molecular conformation of the collagen IV, which might be the molecular basis for pathophysiological changes observed in diabetic microvascular complications.