Computerized image analysis was performed on freeze-fractured nuclei isolated from normal rat liver and rat liver with diethylnitrosamine induced hepatocarcinomas. Chromatin particles belonging to heterochromatin and interchromatin nuclear regions were measured, distributed into histograms and statistically processed. The ratio between nucleosome filaments (5-10 nm range diameter) and solenoid fibres (25-35 nm range) and Tukey's fitting line were calculated. The N/S ratio shows an inverse trend in treated nuclear samples with respect to the controls indicating that the malignancy progression is accompanied by characteristic derangement of the chromatin arrangement which can be evaluated by morphometric analysis.