The DNA content of 48 gastric carcinomas from archival material was analysed by static and flow cytometry. By image analysis 81.3% of the tumours were aneuploid and ploidy was related to stage (P = 0.024) and lymph node metastasis. A trend for better survival (> 12 months) was observed in patients with diploid tumours (P = 0.058). The mean 5c exceeding rate (5cER) was significantly related to tumour stage (P < 0.05) and patient's survival (P = 0.018). In contrast, by flow cytometry only 43.7% of these tumours were aneuploid and these were more often associated with lymph node metastasis (59.3%) but no relationship was observed with any other parameters or patient's survival. In this series, image analysis appears to be more sensitive than flow cytometry in detecting small aneuploid populations. It may give additional prognostic information. It is, however, a time-consuming technique.