We report on a study of 6 cases of Necrotising Sarcoidal Granulomatosis (NSG) and details of another problem case illustrating the difficulties of classification. We have compared the clinical and pathological features with those of sarcoidosis, Wegener's Granulomatosis (WG), Churg Strauss Granulomatosis (CSG), Pulmonary Hyalinizing Granuloma (PHG) and various metal lung diseases. We distinguish NSG from sarcoidosis, in particular by the prominence of vasculitis, necrosis and the rarity of extrapulmonary manifestations, but accept that problem cases can occur. We see no difficulty in separating NSG from CSG, PHG and metal lung granulomatous diseases, but on occasion WG may cause considerable difficulty. For the present NSG is best regarded as a distinct entity.