The prevalence of psoroptic mange (sheep scab), louse infestation and blowfly strike in sheep in Great Britain between March 2003 and February 2004 was investigated by means of a retrospective postal survey, stratified by region. Of the 3530 questionnaires sent out, 1067 were returned completed, a response rate of 30·2 per cent. Overall, 9 per cent of the farmers reported at least one outbreak of scab, 10·7 per cent reported an outbreak of lice and 75 per cent reported at least one case of blowfly strike. A mean of 1·4 per cent of ewes were struck by blowfly and 2·8 per cent of lambs. There were strong regional variations in disease prevalence, with scab and lice infestation being highest in Wales, Scotland and the north of England and blowfly strike highest in the south west of England.