A young man without any past history of note had taken isotretinoin fo
r disfiguring acne before the summer season. He presented with a sever
e bilateral pneumonia, associated with dyspnoea two months after the s
tart of treatment. On the pulmonary radiography there was a bilateral
ground glass appearance which was worse on the right. The elevated lev
el of eosinophils (54% in 564,000 cells/ml) in the alveolar lavage lea
d to a diagnosis of allergic pneumonia. The rapidly favourable outcome
following the cessation of the medication and with the addition of co
rticosteroids seemed to us a supplementary argument in favour of a dia
gnosis of eosinophilic pneumonia, due to isotretinoin which seemed the
primary initiating factor.