Details of cases involving the inadvertent exposure of birds to eight toxic substances are recorded. The organophosphate insecticides dichlorvos, diazinon and malathion produced respiratory symptoms which in the former and latter cases were initially thought to be caused by infectious disease. Birds which consumed feed containing fenitrothion showed nervous signs before death. On three separate occasions feral starlings (Sternus vulgaris) were found dead and their gizzard contents contained mevinphos. The rodenticide warfarin was associated with petechial haemorrhages in the skeletal muscles and on the serosal surfaces of one hen. Cyanogenic glycosides from Eucalyptus cladocalyx were responsible for the sudden deaths of ducks and guinea fowl. 'Ornamental dough' containing sodium chloride was fed to birds which were deprived of water and they showed diarrhoea and nervous disorders before death.