Sinusoidal dilatation found in the absence of an impaired sinusoidal blood outflow has been so far of unclear significance. Sinusoidal dilatation may actually be a nonspecific feature of impaired portal venous blood inflow, whatever the cause, or a feature of severe systemic inflammatory reaction syndrome, whatever the cause. Sinusoidal dilatation is mainly located in the centrilobular area even in the absence of an outflow block. A predominantly periportal location is specifically found in oral contraceptive users, associated with an inflammatory condition. There is strong evidence for the association of sinusoidal dilatation and oxaliplatin-based chemotherapy but not for estroprogestative steroids or thiopurine derivatives. Exposure to anabolic androgen steroids appears to cause sinusoidal changes different from a mere sinusoidal dilatation. Conclusion: There is evidence of activation of the interleukin-6 and vascular endothelial growth factor pathways in sinusoidal dilatation, but the mechanisms linking the activation of these pathways with the microvascular changes must be identified. (HEPATOLOGY 2015;62:956-963) S inusoidal dilatation (SD) in the absence of postsinusoidal outflow block is characterized by enlarged hepatic sinusoids as a predominant histopathological feature.