Transit times of radiopaque markers through the human gut were measured by published techniques and compared with a simplified method. Three sets of distinctive markers were ingested by 24 healthy persons on 3 successive days. In the first part of the study, daily abdominal x-rays were taken and individual stools were collected for radiography. Mouth-to-anus transits were assessed from the fecal output of markers and mean colonic and segmental colonic transits were calculated from the daily radiographs. These established methods were then compared with estimates of total colonic and segmental transits based on a single abdominal film, taken on the fourth day. The single-film technique correlated well with values obtained from the previous, but more inconvenient, methods. Using the simpler approach, colonic transit was assessed in 49 additional healthy subjects, for a total group of 73. Total colonic transit was 35.0 +/- 2.1 h (mean +/- SE); segmental transits was 11.3 +/- 1.1 h for the right colon, 11.4 +/- 1.4 h for the left colon, and 12.4 +/- 1.1 h for the rectosigmoid. Men had significantly shorter transits for the whole colon than did women (p less than 0.05), and this difference was apparent to some extent in the right (p = 0.06) and left colon (p = 0.07) but not in the rectosigmoid. Age did not influence transit significantly nor did a small dose of supplemental fiber. The technique is simple, convenient for clinical usage, and reduces the exposure to radiation to acceptable levels. There should be a role for this approach in the evaluation of colonic transit in selected patients.