PURPOSE To determine the effect of various risk factors on postbiopsy bleeding (PBB). PROCEDURE A retrospective review of 645 native kidney biopsies carried out from 1981 to 2001 was conducted. Data regarding age, gender, race, prebiopsy blood pressure, history of hypertension, pre- and postbiopsy haemoglobin/haematocrit, serum creatinine and blood urea nitrogen (BUN) were collected. FINDINGS The overall PBB complication rate was 6.2%. High blood pressure was associated with a high risk of bleeding (test for trend, P < 0.05). It increased when systolic blood pressure (SBP) was >160 mm of Hg, diastolic blood pressure (DBP) was >100 mm of Hg, or mean arterial pressure (MAP) was > or = 120 mm of Hg. In patients with a history of hypertension, the risk of PBB was 3.74 times higher (P = 0.0001) than patients with no history of hypertension, irrespective of blood pressure at the time of biopsy. For patients with creatinine > 2 mg/dL, the risk ratio for PBB was 5.89 when compared with patients with creatinine < or = 2 mg/dL. Logistic regression analysis showed that a history of hypertension was associated with PBB, with an odds ratio of 1.89 (confidence interval, 1.10-3.26, P < 0.03), and serum creatinine of > 2.0 mg/dL was associated with an odds ratio of 2.56 (confidence interval, 1.48-4.42, P = 0.001) for PBB. CONCLUSIONS The risk of PBB increases with high SBP, DBP or MAP. A history of hypertension and high serum creatinine are significant independent risk factors for PBB.