Eleven cases of thrombocytopenic purpura (TP) in sexually mature male or female Göttingen minipigs occurred sporadically over 3 1/2 years in a closed breeding colony protected by strict barrier conditions. Typical clinical signs of TP, including extensive subcutaneous haemorrhages, were seen in all affected animals. Haematological abnormalities included marked thrombocytopenia and anaemia. A consistent histopathological finding was the presence of membranoproliferative lesions in the renal glomeruli. Immunohistochemically, glomerular deposits were positively labelled for complement factor C1q and often also for immunoglobulins. Bone marrow findings consisting of increased numbers of immature and apoptotic megakaryocytes were compatible with a state of increased platelet consumption. Based on the combined presence of thrombocytopenia and renal immune complexes, it is suggested that the syndrome was related to a type III hypersensitivity reaction. However, further studies are needed to verify this hypothesis.