A randomized controlled double-blind study was undertaken to assess the efficacy and safety of endoscopic neodymium:yttrium aluminum garnet (Nd:YAG) laser therapy for active esophageal variceal bleeding. Ten patients were randomized to the laser treatment group and 10 to a control group that received sham endoscopy and standard medical therapy. Initial hemostasis was achieved in seven laser-treated patients but in 0 of 10 controls receiving sham treatment (p less than 0.002). However, four of the seven who were initially controlled with laser therapy had rebleeding 12 to 48 hours later; thus, three of 10 laser patients had lasting hemostasis. The mean blood transfusion requirements were similar in both groups (laser = 7.3 units; control = 7.8 units). Six of the 10 laser-treated patients were discharged from the hospital and four died. There were seven hospital deaths in the control group and three patients were discharged (p = 0.22). In two patients in the treatment group, laser therapy increased bleeding. There were no perforations.