A patient is reported presenting a cerebellar disorder developing about 5 weeks after acute exposure to an organophosphate insecticide. Initially no major cholinergic features were observed. The ataxia of delayed onset was not accompanied by clinical or electrophysiological signs of polyneuropathy. The possible pathogenetic mechanisms are reviewed and discussed. This case illustrates the need to closely monitor all patients intoxicated with such chemicals for at least 5 weeks. One should not only keep in mind the well-known late-onset polyneuropathy, but also the less frequent delayed central nervous system effects, even in the milder cases where initial signs of acetylcholine excess are only minimally present or lacking.