In a prospective study of 36,728 women and 35,688 men during 18 years of follow-up, compared to systolic pressure <130 mm Hg, levels of 130-149, 150-169 and >or=170 mm Hg in women were associated with relative risks of renal cell cancer of 1.7, 2.0 and 2.0, respectively (P for linear trend, 0.11). In men, there was no association with blood pressure.