To determine if there are therapeutic advantages to oil-soluble contrast medium compared with water-soluble medium during hysterosalpingography.A randomized, controlled trial including 56 infertile patients undergoing hysterosalpingography was performed. After a hysterosalpingogram with water-soluble contrast demonstrated tubal patency, 30 patients were randomized to receive oil-soluble contrast medium (oil group) and 26 patients received no additional contrast medium (control group). The outcome was pregnancy and timing of pregnancy in relation to hysterosalpingography. There were 18 (64%) pregnancies in the oil group and 14 (56%) pregnancies in the control group. Mean time to achieve pregnancy was shorter in the oil group: 3.8 months in the oil group compared with 6.1 months in the control group (P =.06) There was a clinically meaningful improvement in pregnancy rates between the oil group and the control group at 1 month postprocedure (relative risk [RR] 2.1, 95% confidence interval [CI] 0.6, 7.2). However, at 12 months postprocedure, the advantage was diminished. (RR 1.3, CI 0.8, 2.1)Eighteen months after hysterosalpingography, contrast does not appear to influence cumulative pregnancy rates; however, the addition of oil-soluble contrast medium to water-soluble contrast medium may have the potential to reduce the time to conception.