The protein S deficiency is an ischemic stroke main risk factor in black young people. The authors report three patients of 37, 45 and 56 years old of age who presented ischemic stroke with hemi body deficit (two lefts and one right). No personal or family history of any cardiovascular diseases and risk factor were found except protein S deficiency with 15%, 22% and 32%. One died at eight months later of follow up by stroke relapse, the second had completely health recovery after six months, and the third patient remained with partial paralysis. The research of protein S deficiency must be born in mind in patient with ischemic stroke if any other risk factor was not found.