We examined 46 nonalcoholic steatohepatitis (NASH) and 52 hepatitis C virus (HCV) biopsy specimens to determine the magnitude of fibrosis heterogeneity and minimum length for accurate fibrosis staging. Three fibrosis scores were recorded: lowest regional, highest regional, and most common overall. Mean specimen lengths were 1.6 and 1.8 cm in NASH and HCV, respectively (P = .283). Mean (highest minus lowest) fibrosis heterogeneity scores (highest regional fibrosis - lowest regional fibrosis) were 3.7 and 2.0 in NASH and HCV, respectively (P < .001). Of 36 NASH specimens longer than 1.0 cm, 31 (86%) had the highest regional fibrosis in the deepest sampled parenchyma. Shorter specimens were associated significantly with greater fibrosis heterogeneity in NASH (coefficient, -1.3; P < .001) but not in HCV (P = .901). NASH specimens longer than 1.6 cm had significantly lower mean heterogeneity scores than specimens 1.6 cm or shorter (1.2 vs 3.4; P = .012). In NASH, fibrosis heterogeneity can be substantial and is greater than in HCV, and parenchymal injury, fibrosis, and healing might vary in different regions of the liver. The fibrosis stage in patients with NASH might not be assessed accurately in short specimens. Individual needle cores should be longer than 1.6 cm in NASH for accurate fibrosis staging.