Background: Establishing the patency of the fallopian tubes is a commonly undertaken diagnostic investigation for women with subfertility. This is usually achieved by flushing contrast medium through the tubes and taking radiographs. However, it has been noted that many women conceive in the first three to six months after the tubal flushing, which has raised the possibility that tubal flushing could also be a treatment for infertility. There has been debate about which contrast medium should be used (water-soluble or oil-soluble media) as this may influence pregnancy rates. Objectives: To evaluate the effect of flushing fallopian tubes with oil- or water-soluble contrast media on live birth and pregnancy rates in women with subfertility. Search methods: We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register of trials, MEDLINE, EMBASE, Biological Abstracts, trial registers and reference lists of identified articles. The most recent search was conducted in June 2014. Selection criteria: Randomised controlled trials (RCTs) comparing tubal flushing with oil-soluble or water-soluble contrast media, or with no treatment, in women with subfertility. Data collection and analysis: Two authors independently selected the trials, assessed risk of bias and extracted data. We contacted study authors for additional information. The overall quality of the evidence was assessed using GRADE methods. Main results: Thirteen trials involving 2914 women were included, of whom 2494 were included in the analysis. Oil-soluble contrast media (OSCM) versus no intervention The OSCM group had a higher rate of live birth (odds ratio (OR) 3.09, 95% CI 1.39 to 6.91, 1 RCT, 158 women, low quality evidence) and ongoing pregnancy (OR 3.59, 95% CI 2.06 to 6.26, 3 RCTs, 382 women, I2 = 0%, low quality evidence) than women who had no intervention. Our findings suggest that among subfertile women with a 17% chance of an ongoing pregnancy if they have no intervention, the rate will increase to between 29% and 55% if they have tubal flushing with OSCM. Water-soluble contrast media (WSCM) versus no intervention There was no evidence of a difference between the groups in rates of live birth (OR 1.13, 95% CI 0.67 to 1.91, 1 RCT, 334 women, very low quality evidence) or ongoing pregnancy (OR 1.14, 95% CI 0.71 to 1.84, 1 RCT, 334 women, very low quality evidence). OSCM versus WSCM Two RCTs reported live birth: one found a higher live birth rate in the oil-soluble group and the other found no evidence of a difference between the groups. These studies were not pooled due to very high heterogeneity (I2 = 93%). There was no evidence of a difference between the groups in rates of ongoing pregnancy, however there was high heterogeneity (OR 1.44, 95% CI 0.84 to 2.47, 5 RCTs, 1454 women, I2 = 76%, random-effects model, very low quality evidence). OSCM plus WSCM versus WSCM alone There was no evidence of a difference between the groups in rates of live birth (OR 1.06, 95% CI 0.64 to 1.77, 1 RCT, 393 women, very low quality evidence) or ongoing pregnancy (OR 1.23, 95% CI 0.87 to 1.72, 4 RCTs, 633 women, I2 = 0%, low quality evidence). There was no evidence of a difference between any of the interventions in rates of adverse events, but such events were poorly reported in most studies. Authors' conclusions: The evidence suggests that tubal flushing with oil-soluble contrast media may increase the chance of pregnancy and live birth compared to no intervention. Findings for other comparisons were inconclusive due to inconsistency and lack of statistical power. There was insufficient evidence on adverse events to reach firm conclusions. Further robust randomised controlled trials are needed.