SummarySera from 168 submariners, the entire crew of a Polaris submarine, were tested for Coxsackie B Virus (CBV) specific IgM antibodies using a µ antibody capture enzyme linked immunosorbent assay (ELISA). 36 (21%) were positive or weak positive with 22 (13%) confirmed by CBV neutralisation tests (NT) suggesting recent or active CBV infection. The sailors were observed over a two year period during which three patients (2%) developed illnesses suggestive of the post viral fatigue syndrome. These cases, all previously seronegative for CBV did not seroconvert once they became unwell and their illnesses are presumed to have been due to other viruses. The prevalence of CBV infections and the post viral fatigue syndrome in this close and confined community are discussed.