Case histories of three male patients diagnosed as idiopathic retroperitoneal fibrosis either on autopsy or following intra-operative biopsy are reported. Two of them were in the 5th decade and one aged 22 yrs. All of them presented with features of urinary tract obstruction and renal failure. The obstruction was detected either by ultrasonography or following ascending pyelogram. One of them underwent peritoneal dialysis but later on died of sudden cardiac arrest. The remaining two underwent surgery, during which a biopsy was taken. Histological examination in all the three patients revealed fibroblastic proliferation and mononuclear cell infiltration. Features of chronic periaortitis were also found in the autopsy specimen of descending aorta of the first patient. Both the elderly patients had aortic atherosclerosis which is suspected to be the etiological factor for fibrosis. However in the young male patient intense eosinophilic infiltrate was observed in biopsy material pointing towards 'hypersensitivity' reaction as a cause for fibrosis.