Hepatic lipidosis is a well-recognized condition that is frequently diagnosed postmortem in numerous species of reptiles. Unfortunately, there is a paucity of information concerning the pathogenesis of hepatic lipidosis in reptiles, and, until relatively recently, the collection of biopsies for definitive antemortem diagnosis presented a challenge to clinicians. Although many of the difficulties of sample acquisition have now been overcome, the practitioner is still faced with the problems of microscopic (histopathologic and electron microscopic) interpretation. This article clarifies, and attempts to quantify, the diagnosis of hepatic lipidosis so that others may build on this foundation to produce a body of further information on this clinically important condition. A logical case investigation is described, with particular emphasis on histological interpretation through the grading of microscopic lesions. Copyright (C) 2000 by W. B. Saunders Company.