1. An outbreak of ‘Winter Vomiting Disease’ is described involving women at a University Hall of Residence. Of the 165 women exposed, 74 vomited in the first 24 hr., and 17 more over the next 4 days.

2. Public health investigations were negative.

3. On the hypothesis that the vomiting was at least partly hysterical it was predicted that the affected would have higher N scores than the unaffected on the Eysenck Personality Inventory; that they would have a higher frequency of past attendance at the University Health Centre; and that they would be non-randomly distributed through the Hall and its annexes. All these predictions proved to be incorrect.

4. There is some slight but consistent evidence to suggest that there is a neurotic component in the small group of 28 who felt nauseated but did not vomit.

5. The histogram of time of vomiting has two peaks. It is shown that 71 out of the first 74 cases can be accounted for on the hypothesis of contamination of the food at both lunch and dinner on the first day of the outbreak, with the mean response coming 7 hr. after eating.

6. It is suggested that these results make a food-borne agent a more likely explanation of ‘Winter Vomiting Disease’ than the currently favoured airborne virus acting via the central nervous system.

The costs involved in the psychiatric side of this investigation were defrayed by a grant from the Clinical Research Committee of the Middlesex Hospital. We would like to thank the Chairman and members of the Committee for making these funds available and for their interest and confidence. We would also like to thank Dr A. W. Beard, Consultant Physician at the Middlesex Hospital for his advice and support.