SUMMARYCheese made from sheep milk was implicated in food-poisoning incidents in December 1984 and January 1985. Bacteriological examination of batches of cheese failed to reveal a viable pathogen but enterotoxin A produced by Staphylococcus aureus was present. This was the first time that enterotoxin was detected in a food produced in the UK which was associated with poisoning and from which viable Staph. aureus could not be isolated. Subsequent detailed examination of milk, yoghurt and cheese from the same producer revealed that contamination with Staph. aureus was associated with post-infection carriage as well as clinical illness in ewes on the farm. Strains producing enterotoxin A were still intermittently present in the bulk milk used for cheese production nearly 2 years afterwards, apparently in the absence of clinical illness in the sheep. The possible effects of heat treatment are discussed. Any changes in legislation should cover all non-human mammalian milk used for human consumption. THE OUTBREAKOn 31 December 1984 approximately 170 resident guests and 65 non-resident guests attended a Hogmanay dinner in a hotel in Ayrshire. Thirteen residents (three being hotel staff) reported illness, the onset of which varied between 3 and 6 h after the meal. The principal symptoms were of violent vomiting followed by severe diarrhoea. This lasted for 2-6 h and there was rapid recovery. During subsequent enquiries by the local Department of Environmental Health it was found that after a 'gourmet' meal on 5 December 1984 12-14 other persons had suffered similar symptoms. Only smoked scallops and sheep milk cheese were common to both meals, and 6 of the 13 ill on 31 December had not eaten the scallops. Approximately 60 portions of cheese had been served on this occasion, but not all of those present had eaten the sheep milk cheese which was not part of the normal hotel cheese board. Portions of a pasta course, a beef course, a cheese course and a sweet were submitted for analysis to Crosshouse Hospital, Kilmarnock. Environmental swabs from the kitchen were also examined. No pathogen was recovered.The opinions expressed are those of the authors and do not necessarily represent those of their employing authorities.