Although graft vs. host disease (GvHD) is a frequent complication of allogeneic bone marrow transplantation (BMT), involvement of the central and peripheral nervous systems (CNS and PNS, respectively) has not been demonstrated conclusively. Here, we report of a patient who, following allogeneic BMT for lymphoblastic T-cell lymphoma, suffered a syndrome characterized by self-remitting cerebellar and pyramidal signs associated with a progressive involvement of the peripheral nervous system (PNS). Clinical course and laboratory findings correlated with relapses of systemic GvDH, thus suggesting the possibility that involvement of CNS and PNS may be sustained by a similar pathogenic mechanism.