A study of 61 cases of microinvasion of the cervix occurring in our population between 1980 and 1989 is reported. The mean age of the women was 39 years, compared with 30 years for cervical intraepithelial grade 3 (CIN III) and 47 years for frank invasion, respectively. Colposcopic suspicion of microinvasion was present in 31 cases, giving a sensitivity of colposcopic diagnosis of 50% and a specificity of 91%. In 21 cases (34%) there was no suspicion either cytologically or colposcopically of microinvasion. Colposcopy predicted microinvasion more accurately with increasing depth of invasion. In 28 women there had been previous smears within 10 years available for review. The time interval between the first abnormal smear and the histological diagnosis ranged from 1 month to 9.8 years (mean, 4 years).