Two hundred and thirty two patients underwent cervical colposcopy within the first year of establishing a colposcopy service in the sexually transmitted diseases clinic at St Mary's Hospital, London. Their mean age was 27 years. Cervical intraepithelial neoplasia (CIN) was identified in 68 of 81 (84%) patients whose smears showed dyskaryosis and who underwent biopsy. CIN was also detected in 14 of 41 (34%) patients who underwent biopsy and whose repeat smears were reported as giving normal results. The value of assessing two consecutive smears was evident, however, because none of the 99 patients with CIN had two normal smear results consecutively. Patients requiring treatment underwent laser ablation, which was provided in the department of gynaecology. These results show that colposcopy plays a vital part in managing patients with abnormal smears and indicate that genitourinary physicians need to give priority to developing colposcopy services in their specialty.