Myalgic encephalomyelitis is a common disability but frequently misinterpreted. Amongst 6,000 patients referred for general microbiological diagnosis between 1975 and 1987, 420 cases were recognized. Coxsackie B neutralization tests, in 205 of these, demonstrated significant titres in 103/205 (50%), while of 124 additionally investigated for enteroviral IgM, 38/124 (31%) were positive. This illness is distinguished from a variety of other post-viral states by an unique clinical and epidemiological pattern characteristic of enteroviral infection. Prompt recognition and advice to avoid over-exertion is mandatory. Routine diagnosis, specific therapy and prevention, await further technical advances.