Continuous fluid-inflation proctometrograms were performed in men with the symptoms of chronic radiation proctitis and in age and sex-matched control subjects (n = 10). Rectal volumes and compliance were measured. There was a significant reduction in the rectal volumes at sensory threshold, constant sensation and maximal tolerance and in rectal compliance (P less than 0.01). Comparable pressure measurements did not demonstrate significant differences. The maximum tolerable volume, symptomatic and sigmoidoscopic scoring correlated to rectal compliance (r = 0.77, -0.8, -0.73; P less than 0.01, less than 0.01, less than 0.02, respectively). Reduction in volume and compliance is often not obvious radiologically. Histological evidence suggests that smooth muscle hypertrophy and myenteric plexus damage are contributory.