A study was performed on a nonconsecutive series of 5 1 patients in order to assess the feasibility, reliability, and usefulness of flow cytometric (FCM) DNA analysis of samples obtained from benign and malignant hepatic tumours by means of ultrasound-guided fine-needle aspiration (UG-FNA). Cytological and often histological confirmation of the nature of the lesion was obtained in all cases from an expert pathologist. For FCM DNA analysis in 32 cases, it was also possible to use samples obtained at surgery from the actual tumours. There were no post UG-FNA complications, either early or late. It was possible to perform FCM DNA analysis on 617 (85.7%) of the benign tumour aspirates and all 44 (100%) coming from the malignant tumours. All the benign tumours showed a DNA-diploid pattern, while the DNA content was aneuploid in 91% of the malignant tumours. Apart from one case, the results of the FCM DNA analysis of the samples removed at surgery were the same as those obtained from the aspirates (97%). FCM DNA analysis on UG-FNA samples from hepatic tumours is a fairly simple, reproducible, well-tolerated technique; it does not involve risks if performed by skilled operators and, since it can be easily repeated even on small tumours, it is a suitable method for monitoring hepatic metastases during chemotherapy.