Necropsies were performed on 14 psittacine birds of various species suspected to have proventricular dilatation disease (PDD). Eight of the birds exhibited neurological signs (seizures, ataxia, tremors and uncoordinated movements) and digestive tract signs (crop stasis, regurgitation, inappetance and presence of undigested food in the faeces). At necropsy, the birds had pectoral muscle atrophy, proventricular and ventricular distention, thinning of the gizzard wall, and duodenal dilation. In addition, five birds had a transparent fluid (0.2 to 1.0 ml) in the subarachnoidal space of the brain, and one bird had dilatation of the right ventricle of the heart. The histological lesions differed from earlier reports of PDD in that peripheral (sciatic, brachial and vagal) neuritis was seen in addition to myenteric ganglioneuritis, myocarditis, adrenalitis, myelitis and encephalitis.