Percutaneous transluminal angioplasty (PTA) has been shown to cause cracking of the intimo and atherosclerotic plaque in the renal arteries of two cases, who died from incidental causes about a week after the procedure. In addition, movement or redistribution of atheromatous gruel was seen into the cracks and dissections at the intima-medial junction and media. Thus, enlargement of the lumen by redistribution of the lipid mass by 'warm flow' may be an important beneficial result of angioplasty. One case also showed severe fragmentation of medial elastic fibres at the orifice, with rupture of the internal elastic membrane.