Abstract: A method for inhibiting smooth muscle cell proliferation in an injured blood vessel includes the steps of administering a photoactivatable psoralen to a patient in an amount to achieve local arterial tissue levels of psoralen suitable for light-dependent inhibition of smooth muscle cell growth, and delivering radiation in the visible wavelength range to the injured region of the blood vessel at a level sufficient for photoactivation of the psoralen. The psoralen is preferably 8-methoxypsoralen and can be delivered systemically or locally. The method of the invention can be used for preventing restenosis in a blood vessel following transluminal angioplasty. Both the psoralen and the visible light can be delivered with a laser balloon catheter having a porous balloon. The method of the invention may also be used for inhibiting proliferation of other undesired cell types in a patient's body.