1. Sixteen cases of paralytic poliomyelitis and twenty-four cases of aseptic meningitis (‘non-paralytic poliomyelitis’) occurring in the Sheffield area were studied clinically and by virological methods.
2. Poliovirus was isolated from thirteen of the sixteen cases of paralytic poliomyelitis and from three of the twenty-four cases of aseptic meningitis. In another two of the cases of paralytic poliomyelitis and another six of the cases of aseptic meningitis serological evidence of poliovirus infection was obtained.
3. Serological evidence of Coxsackie virus infection was found in four of the cases of aseptic meningitis; but in one there was also clear-cut evidence of poliovirus Type 3 infection, and in another it seemed that the infection was contracted in hospital. Evidence of Coxsackie virus infection was also obtained in five cases of paralytic poliomyelitis.
4. Serological evidence of Adenovirus infection was found in one case of aseptic meningitis.
5. No acceptable evidence was found of infection with Columbia SK or related viruses, or with the virus of lymphocytic choriomeningitis.
6. From one patient with aseptic meningitis an unidentified virus was isolated.
We wish to thank Dr J. Kennedy for permission to study patients and Prof. C. P. Beattie and Prof. C. H. Stuart-Harris for help in preparing the manuscript.