After liver transplantation (LT), hepatic veno-occlusive disease (VOD), which is also known as sinusoidal obstruction syndrome (SOS), has been reported initially in relation to azathioprine use and subsequently in relation to acute rejection (AR). Isolated veno-occlusive disease (iVOD)/SOS raises some questions about its significance and especially its treatment. From the post-LT biopsy samples of 1364 patients (2000-2008), 31 patients with index biopsy samples showing VOD/SOS (2.3%) were identified. After a review of the index biopsy samples and previous biopsy samples, those patients not exposed to azathioprine therapy were subdivided into 2 groups according to the absence or presence of AR. Fifteen of the 31 patients had no previous evidence of AR, whereas 16 experienced episodes of AR (before or concurrently with VOD). The 2 groups were similar in terms of demographic and clinical data and the range of histological centrilobular changes. AR episodes were characterized by an endothelial predilection. iVOD/SOS occurred later than acute rejection-related veno-occlusive disease (AR-VOD)/SOS (mean times of 65 and 4.4 months, respectively, P ¼ 0.0098). There was a tendency for iVOD/SOS to progress less frequently to chronic rejection in comparison with AR-VOD/SOS (3/15 versus 9/15, P ¼ 0.06). The histological resolution of iVOD/SOS was significantly more frequent in patients who benefited from increased immunosuppression in comparison with those who did not (5/7 versus 2/8, P ¼ 0.05). When the groups were considered together, the same result was obtained (14/18 versus 4/12, P ¼ 0.024). In conclusion, despite a constant overall prevalence of VOD/ SOS, the proportion of iVOD/SOS has increased. The histological resolution of iVOD/SOS after increase in immunosuppression suggests an immune-mediated origin. Better optimization of immunosuppression may be a curative treatment.