Both flow cytometry (FCM) and image cytometry (ICM) were used to assess the DNA content of 1864 lesions (benign and malignant tumors, dysplasias, dystrophies and normal tissue). In total there were 1274 cases of bladder washings and 590 fresh solid tumor specimens. Of the total number of specimens, 1737 (93.2%) were satisfactorily assessed by ICM and 1424 (76.4%) by FCM. In only 100 (5.4%) cases was the DNA content unable to be assessed by either method. When bladder washings were excluded, 99.5% of samples could be evaluated by one method or the other. Concomitant determinations with both technologies were made in 1397 cases. When comparing all evaluable cases, concordance between the ploidy measurements of FCM and ICM was 92.8% (1297 concordant cases out of 1397). When bladder washings were excluded and only solid tumors considered, the concordance was 96.1% (545 concordant cases out of 567). From the experience of applying ICM and FCM to the 1864 lesions the technical limitations of each method became evident, specifically the problems of doubtful DNA diploidy and doubtful DNA aneuploidy. When there were 'doubtful' ploidy findings, the cause was generally found to be morphologic alterations of the nuclei or differences in staining procedures employed, and often the complementary use of both FCM and ICM provided ploidy clarification in questionable cases.