To determine whether semiquantitative glucose measurements of spot urine specimens accurately reflect prevailing plasma glucose levels, reported levels from 400 2nd-voided urines were compared to simultaneous plasma determinations from 246 human adult diabetics. Quantitative urine levels and plasma glucose levels correlated. When semiquantitative urinary determinations were compared to plasma glucose stratified into 0-149, 150-199, and greater than 200 mg/dl, 75% of the urine samples associated with plasma levels from 150-199 mg/dl were negative by Diastix, and 16.5% of samples negative by Diastix were in the 200 + mg/dl plasma range. Only 9% of samples from 0-149 mg/dl showed any positive Diastix readings. Because of the low sensitivity of semiquantitative methods, spot urine glucose determinations except for detection of marked hyperglycemia, are inadequate as the sole means of clinical assessment for management of diabetic patients. Home glucose monitoring may be a better alternative for follow-up of these patients.