Two epidemics of meningoencephalitis caused by echovirus type 7 and coxsackievirus type B 5 in the summer and autumn of 1973 in Umeå in Northern Sweden were compared. Most patients with echovirus 7 meningoencephalitis were neck stiff and 50% had a polymorphonuclear pleocytosis in the cerebrospinal fluid (CSF). The illness was usually mild. It appears to be the first time that an epidemic caused by this virus is described from Scandinavia. On the other hand most patients with coxsackievirus B 5 meningoencephalitis showed a more profound involvement of the central nervous system, with abnormal electroencephalograms in 70% and a long convalescence period. The number of cells in CSF was normal in 70% of these patients.