Urinary microalbumin was detected by an autoanalyzer with the method of immunoturbidimetry. The spot urine samples from a group of 140 healthy subjects were determined to establish a reference range of urinary microalbumin excretion rate(confidence interval 95%)and its upper limit was 2.83 g/mol creatinine. This assay and the urinary enzyme(N-acetyl-beta-D-glucosaminidase,NAG)determination were applied in the patients with diabetes mellitus and with hypertension for detecting the incipient nephrological changes. The results showed that this index was sensitive to detect the early elevation of albumine excretion in urine and has been proven to be a more valuable diagnostic tool in the early diagnosis of renal damage than the tradtional urine protein test. As the urinary lysosome enzyme (e.g.NAG) is more specific and sensitive marker of renal tubular injury. it is suggested to combine the microalbumin and the enzyme assays to yield more valuable informations. The serum type Ⅳ collagen determination with the enzyme immunoassay was performed simultaneously in the same group of patients with diabetes mellitus. It was found that the mean value of serum type Ⅳ collagen was higher than that of the control group. This index indicated the dynamic process of collagen peptide synthesis occurred in the basement membrane.