SummaryEight workers employed in a food manufacturing factory presented with symptoms of rhinorrhoea, dyspnoea and wheezing, originating during the preparation of dried mushroom soup. Five had positive immediate skin tests to dried mushroom extract and in four the FEV1fell by over 30% following a bronchial challenge with mushroom dust. The features detected were those of a type I allergic response, without evidence of the extrinsic allergic alveolitis described in ‘mushroom worker's lung