Eight hundred ninety-four women with cytologically diagnosed moderate cervical dysplasia were followed by cytology without major treatment. The results were regression in 54% (follow-up 78 months), progression in 30%, and persistence in 16%. Biopsies were performed in 54%. Results in patients without biopsies were regression in 50%, progression in 35%, and persistence in 15%, implying a statistically significant difference between biopsied and nonbiopsied lesions. Fewer lesions progressed in patients age 51 or older than in younger patients, the progression time also being significantly longer. The cytology periodically returned to normal for more than 12 months in 3.8% of patients with persisting moderate dysplasia. Life table analysis indicated the risk of progression of moderate dysplasia to be 5 to 9/100 women/year. A comparison with the incidence of carcinoma in situ, 4/100,000 women/year, illustrates the yearly progression risk for a cervix with moderate dysplasia as 2000 times greater than for a woman without cervical dysplasia.