The effects of age, gender, and parity on rectoanal function were examined in a cross-sectional population study, including 68 normal subjects (32 men and 36 women) aged 23 to 91 years. Rectal volumetry was evaluated with graded isobaric rectal distension with 5-60 cm H2O in combination with anal manometry. Data were analysed by use of the multiple regression technique. Increasing age correlated with a decrease in rectal volume (r = -0.285, p less than 0.05), resting anal pressure (r = -0.625, p less than 0.001), and maximal squeezing pressure (r = -0.557, p less than 0.001). The decrease in maximal squeeze pressure with age was similar in men and women (approximately = 1% x year-1), although the median of maximal squeeze pressure in women was 58.3-75.7% of that in men (p less than 0.001). Nor was there a difference in resting anal pressure between men and women. An age-dependent increase was observed for the pressure threshold to produce an initial sensation of rectal filling and the rectoanal inhibition reflex (r = 0.446, p less than 0.001). The sensory threshold increased with age, but this was more pronounced in women. No effect of parity on rectoanal function could be demonstrated. However, this would best be investigated in a longitudinal population study. We believe that identification of causes for interindividual variation and regression analysis procedures will increase the discriminative accuracy of analysis of rectoanal function. The present study shows that several of the demonstrated age-related changes have a tendency to expose elderly subjects, particularly women, to the problems of incontinence.