An epidemiologic sample (n= 285) drawn from the population of Skellefteå, Sweden, was examined to evaluate the prevalence of signs and symptoms of craniomandibular disorders (CMD) at the age of 17 years. The sample was then followed up prospectively at the ages of 18 and 19 years. The year they reached 28 years of age a questionnaire concerning prevalence, incidence, frequency, duration, location, and intensity of symptoms of CMD was sent to the same subjects. Two hundred and thirty-four subjects responded (82%). The number of subjects who participated in all examinations (at the ages of 17, 18, 19, and 28 years) was 215 (107 women and 108 men). During the 10-year period from the late teens onwards, a significant increase in reported symptoms of CMD occurred in both men and women. Forthewhole sample the prevalence increased from approximately 20% to 37%. The incidence of CMD symptoms at the age of 28 years was 6% in both sexes. Although fluctuations of symptoms during the period from the age of 17 to 28 occurred in both sexes, the course of CMD in men and women differed significantly. All women who consistendy reported symptoms at the age of 17-19 years also reported symptoms at the age of 28 years; the corresponding figure for men was 60%. At the age of 17 years 25 women reported CMD; 23 of these reported CMD at the age of 28 years (92%). At the age of 17 years 17 men reported CMD; 5 of these reported CMD at the age of 28 (29%). The result indicates different courses for CMD in men and women.