Forty one patients with bleeding vascular ectasias of the upper gastrointestinal tract who required blood transfusion were treated with endoscopic Nd:YAG laser photocoagulation and followed for 34 months (median). Four distinct groups of patients were identified. There was a sustained reduction in transfusion requirements after laser treatment in all those with single (nine patients) and multiple (seven patients) angiodysplasia, in 12 of 16 (75%) patients with watermelon stomachs, and in six of nine (66%) patients with hereditary haemorrhagic telangiectasia. Overall, 25 patients (61%) required minimal or no transfusion after treatment and nine (22%) whose bleeding was controlled initially, later developed recurrent bleeding which was controlled with further laser (total 34 of 41, 83%). Surgery succeeded in a further three patients (7%) in whom laser had failed (in one case possibly because of laser induced haemorrhage). Five more cases of possible laser induced haemorrhage resolved with conservative treatment. One patient sustained a treatment related perforation and died: one patient with cirrhosis died of encephalopathy within one month of starting laser treatment. In two patients transfusion requirements were unchanged despite laser. Nd:YAG laser is a safe and effective treatment for most patients with upper gastrointestinal angiodysplasia.