The purpose of this prospective study was to determine whether tumor ploidy or S-phase fraction measurements were of prognostic value in predicting short-term recurrence for colorectal carcinoma. A total of 52 patients underwent curative resection of colorectal carcinoma. Fresh suspensions of tumor cells were used for flow cytometric analysis. Patients underwent follow-up for possible recurrence, which then was related to ploidy status, S-phase fraction measurement, adjuvant therapy received, and Dukes stage. Disease-free probability was determined using Kaplan-Meier actuarial curves for various subgroups of the study populations. Results revealed that elevated S-phase fraction (>16%) did predict for a higher probability of recurrence in those patients receiving no postoperative adjuvant treatment. Among patients receiving postoperative adjuvant therapy, however, a higher S-phase fraction predicted for a lower probability of recurrence. These data suggest that the S-phase fraction does predict for disease-free probability and also predict response to adjuvant therapy in patients with colorectal carcinoma.