The common clinical and pathological features of polyarteritis nodosa are descriptionbed. Seven cases of polyarteritis nodosa are presented with the clinical and pathological findings. In three cases the diagnosis was only made at autopsy. The first case presented with nephritis and generalised muscular tenderness; the second with mitral stenosis, pleural effusion and mental disturbances; the third as an acute abdominal emergency with massive retroperitoneal haemorrhage. In four cases the diagnosis was made during life. Two cases had typical clinical features and the diagnosis was confirmed by muscle biopsy. One case presented as an acute cholecystitis and the diagnosis was made on microscopy of the gall bladder. The fourth case presented with multiple arterial occlusions. The etiology is discussed and the probable allergic basis is stressed. Attention is drawn to the relationship between polyarteritis nodosa, rheumatic -fever and glomerulonephritis.