The National Health Service Cervical Screening Programme has issued minimum standards for a colposcopy service that facilitates audit. We have looked at the performance of a teaching hospital colposcopy service by analysing the case notes of 639 women who underwent large loop excision of the transformation zone over a nine-month period in 1995. We found delays in patient assessment and communication of results. There was overtreatment, particularly at first visit, and an excessive number of treatments were performed under general anaesthesia. A worrying number of women failed to have a follow up smear performed, but in those that did we found a reassuring treatment success rate. Our findings led to changes in the structure and functioning of the colposcopy clinic that should improve the detection of significant disease and improve the timeliness of diagnosis and the speed with which we communicate results.