Chronic illness played a major role in the life and literary success of Robert Louis Stevenson. However, the exact nature of his chronic illness remains unclear. It is possible that Stevenson had hereditary hemorrhagic telangiectasia (Osler-Rendu-Weber Syndrome). This would explain his chronic respiratory complaints, recurrent episodes of pulmonary hemorrhage, and his death, at age 44 years, of probable cerebral hemorrhage. It would also explain his mother's hitherto unreported but apparent stroke, at age 38 years. Further support for this hypothesis might come from new details about the health of Stevenson and his relatives or from molecular analysis of tissue specimens remaining from him.