Abstract In an outbreak of benign myalgic encephalomyelitis in a girls' school all the residential pupils, both those affected and those unaffected, were investigated. Special virological tests were essentially negative, but it seemed that a few girls had had a viral infection. Psychological testing showed that among younger girls the patients were more neurotic than the others. Girls with various disorders were found to have been classified as having the same disorder, because of what has been called altered medical perception. The conclusions of an international symposium on this condition were not substantiated.