The efficacy of an association of estrogens and progestagens in the treatment of gastrointestinal bleeding by angiodysplasia was analyzed. Thirty-three patients with gastrointestinal bleeding due to vascular malformations were admitted from January 1986 to December 1993. Fifteen of the 33 patients were submitted to surgical or endoscopic treatment. The remaining 18 patients underwent daily oral treatment with a combination of estrogens-progestagens containing 2.5 mg of lynestrenol and 0.075 mg of mestranol. One patient presented a venous thrombosis leading to suppression of treatment at one month of initiation. The 17 remaining patients were treated for a mean of 22 +/- 4 months (range: 3-60). During treatment 13 of the 17 patients (76%) did not present evidence of hemorrhage. Likewise, the number of hemorrhagic episodes per year decreased from 4.4 +/- 1.2 prior to treatment to 0.7 +/- 0.5 during treatment (p < 0.05) with transfusional requirements decreasing from 7.9 +/- 2.8 erythrocyte concentrates per year prior to treatment to 1.2 +/- 1.0 during treatment (p < 0.05). In conclusion, the combined treatment with estrogens and progestagens prevents recurrence of gastrointestinal bleeding by angiodysplasia.