BACKGROUND: A possible therapeutic effect of diagnostic tubal patency testing has been debated in the literature for half a century. Further debate surrounds whether oil-soluble or water-soluble contrast media might have the bigger fertility-enhancing effect. Historically a variety of agents have been used to 'flush' the fallopian tubes, although tubal flushing does not currently form part of routine practice in the treatment of fertility delay. OBJECTIVES: To evaluate the effect of flushing a woman's fallopian tubes with oil- or water-soluble contrast media on subsequent fertility outcomes in couples with infertility. SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility Group's specialised register of trials (searched 2 March 2004), MEDLINE (1966 to Mar 2004), EMBASE (1980 to Mar 2004), Biological Abstract (1980 to Mar 2004) and reference lists of articles. SELECTION CRITERIA: All randomised trials where tubal flushing with oil-soluble contrast media or tubal flushing with water-soluble media was compared with one another or with no treatment were considered for inclusion in the review. DATA COLLECTION AND ANALYSIS: Eleven randomised controlled trials were identified and included in this review. All trials were assessed for quality criteria. The studied primary outcome was live birth (and ongoing pregnancy), with secondary outcomes pregnancy, miscarriage, ectopic pregnancy, treatment complications including pain, intravasation of contrast medium, infection and haemorrhage, and image quality. MAIN RESULTS: Tubal flushing with oil-soluble media versus no intervention (three trials including 381 participants) was associated with a significant increase in the odds of live birth (Peto OR 2.98, 95%CI 1.40 to 6.37) and of pregnancy (Peto OR 3.30, 95%CI 2.00 to 5.43). There were no data from RCTs to assess tubal flushing with water-soluble media versus no intervention. For the comparison of tubal flushing with oil-soluble media versus tubal flushing with water-soluble media (six trials including 1,483 participants), the increase in the odds of live birth for tubal flushing with oil-soluble versus water-soluble media (Peto OR 1.49, 95%CI 1.05 to 2.11) was based on two trials where statistical heterogeneity was present and the higher quality trial showed no significant difference; there was no evidence of a significant difference in the odds of pregnancy (Peto OR 1.24, 95%CI 0.97 to 1.57). The addition of oil-soluble media to flushing with water-soluble media (water-soluble plus oil-soluble media versus water-soluble media alone; three trials including 555 participants) showed no evidence of a significant difference in the odds of pregnancy (Peto OR 1.18, 95%CI 0.82 to 1.70) or live birth (Peto OR 1.06, 95%CI 0.64 to 1.77). Adverse event data were only available for the comparison OSCM versus WSCM: OSCM carried a significantly higher chance of intravasation (Peto OR 5.41, 95%CI 2.57 to 11.37) but a significantly lower chance of immediate pain (Peto OR 0.53, 95%CI 0.34 to 0.84), prolonged pain (Peto OR 0.26, 95%CI 0.15 to 0.45) and post-procedure bleeding (Peto OR 0.22, 95%CI 0.15 to 0.31), and no serious adverse events were reported. AUTHORS' CONCLUSIONS: There is evidence of effectiveness of tubal flushing with oil-soluble contrast media in increasing the odds of pregnancy and live birth versus no intervention. The limited evidence of an increase in the odds of live birth from tubal flushing with oil-soluble contrast media versus water-soluble contrast media must be interpreted cautiously. Further robust randomised trials, comparing oil-soluble versus water-soluble media and comparing water-soluble media versus no intervention, would be a useful further guide to clinical practice. Further research is merited to ascertain the mechanism of the fertility enhancing effect of oil-soluble media, as to whether this is a 'tubal flushing' phenomenon, an effect on the intraperitoneal environment, or an implantation enhancing effect on the endometrium.