Intrauterine insemination (IUI) is a recognised treatment for infertility. The overall success rate of IUI remains controversial and depends on several factors. There is a wide variation in the practice of IUI across the country. A postal survey was conducted to determine the attitudes to the factors influencing IUI practice. A questionnaire containing 22 factors was sent to 150 reproductive medicine units in the UK. Practitioners were requested to rate each parameter on the scale of 1-10, where 1 was least important and 10 very important. A total of 101 practitioners replied. Over 50% of the corresponding practitioners were Consultants, 32% were Infertility Nurse Specialists and 12% were other clinicians. The factor with the highest rating was the number of the follicles on the day of human chorionic gonadotrophin (hCG) injection, followed by the size of the follicle and the total sperm count. The fourth critical factor voted was the need for a standardised protocol for all the unit staff. The wide variation in the approach to IUI probably explains the great variance in pregnancy rates. Further properly designed studies are needed to ascertain the role of the factors in determining the success of IUI and the most successful protocols.