Neurological complications of 5-fluorouracil (5-FU) chemotherapy are uncommon events. The two patients presented demonstrate two manifestations of 5-FU neurotoxicity, namely a cerebellar syndrome in association with global motor weakness and bulbar palsy, and a bilateral third cranial (oculomotor) nerve palsy. Both highlight the rapid onset and severity of these unusual side effects but also emphasize that, unlike paraneoplastic syndromes or central nervous system involvement by tumour, complete spontaneous recovery is a potential outcome.