Several retrospective studies suggest that abnormal deoxyribonucleic acid (DNA) content in colorectal carcinoma correlates with adverse clinical outcome. Many of these studies have used naked nuclei retrieved from formalin-fixed, paraffin-embedded tissues for flow cytometry. The purpose of this study was to prospectively analyze 137 colorectal carcinomas using fresh whole-cell suspensions for flow cytometry and to determine whether abnormal DNA content (DNA aneuploidy or tumors with high proliferative activity) correlates with Dukes' stage, histologic grade, lymphocytic infiltration of the tumor, tumor fibrosis, extramural venous spread, or tumor size. Cell suspensions for flow cytometry were prepared by enzyme disaggregation with collagenase XI, DNase, and trypsin. Satisfactory DNA histograms were obtained from 132 of the 137 samples. The mean coefficients of variance for the G1/G0 of the external 2C control, internal 2C populations, and aneuploid populations were 2.5, 3.5, and 3.5, respectively. The mean percentage of viable cells was 97%. Of 132 cases, 102 (77%) demonstrated abnormal DNA histograms, of which 77 (58%) showed DNA aneuploidy. Abnormal DNA histograms of DNA aneuploidy did not correlate with Dukes' stage. Tumors of higher histologic grade were more likely to demonstrate DNA aneuploidy, however, these differences did not reach statistical significance. The authors conclude that (1) satisfactory DNA histograms can be obtained with the use of a fresh, whole-cell technique; (2) abnormal DNA histograms did not statistically correlate with standard clinical, grading, or staging parameters; and (3) carcinomas of high histologic grade showed an increased proportion of aneuploid DNA histograms, but this trend did not reach statistical significance.