The ploidy profiles of benign and malignant tumours can be obtained using image analysis. However, the results of ploidy studies have varied according to the type of specimen used. We compared the ploidy profiles of paraffin embedded thin sections, cytospin preparations of disaggregated cells, and cytological smears from the same specimen as defined by image analysis. Ten benign breast lesions, 10 breast carcinomas and 10 malignant melanomas were investigated in this way. Preparations stained by the Feulgen technique were examined using the MD20 video image analysis densitometry system. Ploidy profiles were obtained by measuring the integrated optical density of at least 200 nuclei. By paying proper attention to the quality of fixation and presence or absence of cytoplasm around cells, comparable results were found for all preparations in each case. We therefore conclude that if careful attention is paid to the technical quality of the material, reliable ploidy results can be obtained by image analysis.