Key PointsQuestionCan modulators of cerebrovascular endothelial function, including isosorbide mononitrate (ISMN; a nitric oxide donor) and cilostazol (a phosphodiesterase-3 inhibitor), improve long-term outcomes after lacunar ischemic stroke?FindingsIn this randomized clinical trial of 363 participants treated with ISMN, cilostazol, ISMN-cilostazol, or no study drug in a 2 × 2 factorial design, 99% of patients were retained at 1 year with good study drug adherence and no safety concerns. Isosorbide mononitrate reduced recurrent stroke and cognitive impairment, cilostazol reduced dependence, and ISMN-cilostazol reduced the composite of adverse vascular, dependence, and cognitive outcomes.MeaningThese 2 inexpensive licensed medications (ISMN and cilostazol) may reduce adverse long-term outcomes of lacunar ischemic stroke, a form of cerebral small vessel disease, and definitive trials are needed to confirm these findings.