In October 1976 an epidemic of 120 cases of paralytic shellfish poisoning was recorded in western Europe. Analysis of the 23 cases seen in Swizterland shows the following data; paresthesia of mouth and lips (100%); cerebellar syndrome (86%) with giddiness, ataxia, dysmetry and floating sensation; paresia or paralysis (62%); digestive symptoms (14%); no death. The mean incubation time is 3 hs 30 min; mean duration of the symptoms is 2 days. Half of the patients complain of asthenia and moderate memory disturbance lasting up to 3 weeks. The severity of the illness is in relation to the amount of ingested neurotoxin. The epidemiologic study shows that all European cases were due to consumption of mussels from the Atlantic coast of Spain.