Increased urinary activity of N-acetyl-beta-D-glucosaminidase (NAG) has been reported in many clinical conditions, including essential hypertension. Since hypertension is increasingly recognized as beginning in childhood, we hypothesized that urinary NAG changes with increasing blood pressure may start early in life and may also be the evidence of the existence of early hypertensive disease. We analyzed the urinary NAG changes in 980 young adults, ages between 18 to 32, in relation to age, race, sex, and systolic and diastolic blood pressure. We observed that black women had the highest level of NAG, with or without adjustment for creatinine. With aging, urinary NAG significantly increased in men. As blood pressure increased, urinary NAG excretion appeared to increase, and this was more apparent in black women (P <.05). Significant correlations between NAG excretion and systolic (r = 0.12, P =.04) and diastolic (r = 0.18, P = .003) blood pressures existed in the oldest age group, 28 to 32 years old. These findings show that a significant association between urinary NAG and blood pressure exists in normal young adults and changes in urinary NAG may be evidence of early hypertensive disease.