Corneal argon laser photocoagulation (CALP) was used in 13 patients to treat deep stromal vascular ingrowth. Eight patients had undergone successful penetrating keratoplasty but had developed deep stromal vessels into the graft associated with signs of graft rejection, which did not improve with steroid treatment alone (group 1). After CALP, there was marked regression of the neovascularization with reversal of graft rejection in all eyes. Three additional patients with vascularized corneas, referred for penetrating keratoplasty, underwent CALP preoperatively with obliteration of the vessels (group 2). Two of these patients have since undergone keratoplasty and, in both, the grafts have remained avascular and clear over a 21-month follow-up. Two other patients with corneal injury and progressive corneal opacification and vascularization have also been treated with CALP (group 3). CALP may be a useful adjunct in the treatment of corneal neovascularization. Further clinical studies are needed to define its exact role.