Five hundred and fifty-five women with cervical cytologically diagnosed mild cervical dysplasia were followed by cytology without major treatment. Biopsies were performed in 14% resulting in no significant influence on the outcome of the studied material. Regression to normal occurred in 62% (follow-up 39 months), progression to severe dysplasia/carcinoma in situ/invasive carcinoma in 16% (invasive carcinoma: two patients), and persistence of dysplasia in 22%. Life table analysis calculated the risk of progression of mild dysplasia to be 250 to 800/100,000 women/year. A comparison with the incidence of carcinoma in situ, four of 100,000 women/year, illustrates the yearly risk for a woman with mild dysplasia as 560 times greater than for a woman without cervical dysplasia to develop severe dysplasia/carcinoma in situ/invasive carcinoma.(Obstet Gynecol 67:665, 1986)