In vitro fertilization and embryo transfer (IVF-ET) was the earliest of the assisted reproductive technologies. In Canada, it remains the most commonly practiced technique of assisted reproduction. IVF-ET is a technology which continues to evolve. IVF-ET has diffused widely without comprehensive assessment of its efficacy and safety. Most of the published reports concerning results with IVF-ET as a treatment of infertility have been based upon small, uncontrolled studies. Investigators have used different designs, treatment protocols, patient populations, sample sizes, definitions of outcome measures and types of outcome. Long-term, well-designed, prospective controlled clinical trials are required to determine when and for what indications IVF-ET is effective and what its long-term health effects are on both mothers and their babies. Reliable conclusions cannot be drawn on the effectiveness of IVF-ET for most indications. The available evidence supports the use of IVF-ET as a treatment of infertility related to damaged, occluded or absent Fallopian tubes. For other indications, the present evidence does not establish whether IVF-ET is more effective than receiving conventional treatment or no treatment at all. Obstetric and pediatric complications following IVF-ET may be significant.