Psychiatric manifestations of familial spastic paraplegia are rare and have been described only infrequently. A 35-year-old male is reported, who presented both hypomanic behaviour and gait disturbances as features of a previously undiagnosed familial spastic paraplegia. This association implies that the CNS manifestations of familial spastic paraplegia may overlap with the neurochemical or neuroanatomic substrata regulating mood.