I studied the relation between a maternal history of subfertility and the risk of congenital urinary tract anomalies (CUTAs) in a case-control study. I defined subfertility as having unprotected intercourse for more than 12 months without getting pregnant at any time before the conception of the index pregnancy. A maternal history of subfertility was associated with a slightly increased risk of CUTAs (adjusted odds ratio (OR) = 1.4, 95% confidence interval (CI) 0.8-2.4). Risk was higher for mothers whose subfertility occurred at 20 years of age or younger (OR = 2.2, 95% CI 1.0-4.9). The effect of a maternal history of subfertility on the risk of CUTAs was exacerbated by maternal smoking during the index pregnancy and by an early onset of smoking history.