Fibronectin and factor VIII-related antigen (VIIIR: AG), which are produced by the endothelium and are involved in cellular adhesion, may have a role in the development of diabetic retinopathy. We have measured plasma levels of these glycoproteins and of fibrinogen in 9 control males, 10 insulin-dependent diabetic males with nil or minimal retinopathy and 10 insulin-dependent diabetic males with proliferative retinopathy. These three groups were closely matched for age, body weight and smoking habit. The diabetics in each retinopathy group had similar duration of disease and insulin doses. There was no significant difference between plasma fibronectin concentrations in the three groups. Both plasma factor VIII-related antigen activity and fibrinogen concentration were higher amongst the diabetic subjects, especially those with proliferative retinopathy. These two latter measures correlated significantly when the diabetics were considered as a single group, whereas they did not correlate with fibronectin. Plasma concentrations of fibrinogen and factor VIII R: AG, but not fibronectin, have an association with diabetic microvascular disease.