The albumin index (mg/g·creatinine) was determined in untimed spot urine collected in the early morning from 92 randomly selected outpatients with noninsulin-dependent diabetes mellitus (NIDDM). The patients were divided into three groups: 49 patients with normo-albuminuria (albumin index less than 9.1), 24 with micro-albuminuria (albumin index between 9.1 and 100), and 19 with overt-albuminuria (albumin index over than 100). With diabetic duration, the frequency of the patients with overt-albuminuria was increased, but that with normo-albuminuria was decreased. The patients treated with only a diet almost showed normo-albuminuria. In contrast, microand overt-albuminuria were found more frequently in the patients treated with oral hypoglycemic agents or insulin. Micro- and overt-albuminuria were found more frequently in the patients with poor glycemic control than in those with good glycemic control. The urinary albumin index was significantly high in the micro-albuminuric patients with poor glycemic control. Similarly, micro- and overt-albuminuria were found more frequently in the patients associated with diabetic retinopathy or neuropathy than in those without diabetic complications. In addition, overt-albuminuria was found more frequently in the patients with hypertension. The urinary albumin index was significantly high in the overt-albuminuric patients with hypertension. In conclusion, the determination of the albumin index in spot urine may be convenient and clinically useful for the evaluation of diabetic nephropathy in outpatients with NIDDM.