Serum levels of type IV collagen (7S-IV) and laminin P1 in 185 non-insulin-dependent diabetes mellitus patients were significantly higher than those in normal subjects. Furthermore, they were significantly elevated in relation to the excretion of urinary albumin, showing their increases even at the stage of microalbuminuria, although they were not correlated with HbA1c or age in diabetic patients. Thus, the determination of serum levels of basement membrane components, 7S-IV and laminin, could be beneficial as the early indices of diabetic microangiopathy, including diabetic nephropathy.