There is little information on the characteristics, management, or sequelae of gross hematuria in autosomal dominant polycystic kidney disease (ADPKD). Therefore, we obtained detailed information regarding gross hematuria in 191 adult ADPKD subjects. Forty-two percent (N = 81) experienced at least one episode of gross hematuria. The mean age of the initial episode was 30 +/- 1 years; only 10% of subjects reported the first episode before age 16. Twenty-three percent of those with gross hematuria had experienced more than six occurrences. Sixty-two percent of patients with bleeding indicated a presumptive precipitating event, most commonly urinary tract infection (42% overall, 61% of females v 17% of males, P less than 0.01), or sports or strenuous activity (20% of males v 11% of females, NS). In 56% of subjects, the episode persisted for 2 to 7 days. Hypertensive ADPKD subjects were more likely to have gross hematuria than normotensive subjects (48% v 30%, P less than 0.02) and those with gross hematuria had larger renal size (820 +/- 87 v 588 +/- 52 cm3, P less than 0.03). Moreover, those subjects with more episodes of gross hematuria had a higher serum creatinine concentration than those with fewer episodes (serum creatinine: 0 episodes, 120 +/- 10 v greater than 5 episodes, 190 +/- 30 mumol/L, P less than 0.04 [1.4 +/- 0.1 v 2.1 +/- 0.3 mg/dL]). This association suggests that, although self-limited, cumulative episodes of gross hematuria may have an unfavorable impact on long-term renal function.