A retrospective study was performed of 1832 consecutive in vitro insemination (IVF)/intracytoplasmic sperm injection (ICSI) cycles over 18 months, to analyse the benefits or otherwise to the patient of continuing with in vitro treatment or converting the assisted conception cycle to intrauterine insemination (IUI). Two hundred and seventy cycles were identified in which three follicles or fewer were obtained after controlled ovarian hyperstimulation; in 143 of these cycles, the clinicians or patients elected to abandon all treatment, whereas treatment was continued in 127 patients. In 79 cycles, the patients proceeded with IVF/ICSI and in 48 patients, the cycles were converted to IUI. Data were analysed with regard to the clinical pregnancy rate. In addition, the data for IUI were compared with eight cycles of supraovulation IUI (S/IUI) performed over the same period. There were no significant differences in clinical pregnancy rates among any treatment modality 6/48 (12.5%), 6/79 (7.7%) and 1/8 (12.5%) for IUI, IVF and S/IUI, respectively (P = 0.64). The lowest total number of motile spermatozoa required to achieve pregnancy using IUI was 2.0 × 10⁶. In conclusion, it appears that, if the treatment is suitable, patients who respond poorly to controlled hyperstimulation for IVF would not be disadvantaged in achieving a pregnancy by offering them conversion to the medically and financially less interventional IUI.