OBJECTIVE: To analyze the morphological characteristics of hepatocyte nuclei and to employ stereoscopic parameters to evaluate the exposure to the fungicide Captan. STUDY DESIGN: A clinical trial with 2 groups: G1 (n=7, diet+500 ppm of Captan/kg of feed) and G2 (n=7, diet+500 ppm of kaolin [placebo]/kg of feed). The experimental period was 49 days, all events were individually recorded, procedures were masked, and after that period the animals were sacrificed. Samples were analyzed microscopically, qualitatively, and quantitatively using the following staining: hematoxylin/eosin, periodic acid- Schiff, Prussian blue, and Picro-Sirius. All analyses were evaluated in ImageJ. The relationship between histological grading and related parameters was statistically analyzed. RESULTS: The results demonstrated changes in the size, shape, and position of the hepatocyte nucleus in G1 as compared to G2 (p<0.05); this morphological change is called anisonucleosis. CONCLUSION: Morphological and stereological characteristics demonstrated hepatic anisonucleosis, an initial pathological alteration demonstrating one of the first effects of Captan on the liver of pigs. © Science Printers and Publishers, Inc.