Asymptomatic urinary abnormalities are one of the most frequent abnormalities in clinical nephrology. Between April 1981 and February 1999, we conducted retrospective follow-up studies of 159 patients with asymptomatic urinary abnormality that was proven by kidney biopsy, and evaluated their histologic findings and natural course. Mean age was 34.7 years old and sex ratio of male to female was 78: 81. They were divided into three groups according to the initial urinalysis findings' six patients with isolated hematuria, 33 patients with isolated proteinuria, and 120 patients with concomitant hematuria and proteinuria. The mean follow-up period was 35.5+/-30.5 months. In pathologic findings, 95 cases(59.3%) had IgA nephropathy, 27 cases(17.5%) had minor lesion, 12 cases(7.5%) showed focal and segmental glomerulo- sclerosis, 10 cases(6.3%) had membrannvs glomer-ulonephritis, 9 cases(5.6%) had mesangial prolifera- tive glomerulonephritis. Amyloidosis and thin base-ment membrane disease were seen in two cases, respectively. There were no specific correlations between morphologic patterns and degree of proteinuria. During the mean follow-up period, hematuria or proteinuria disppeared in 14%, persisted in 49%, and developed renal insufficiency in 21%. During the mean follow-up period, isolated proteinuria disappeared in 24%, persisted in 36%, and developed renal insufficiency in 21%. We conclude that the most common cause of asymptomatic urinary abnormalities was IgA nephropathy and early diagnosis through renal biopsy and management is needed to prevent or slow the progression to chronic renal failure.