Studies show that Platelet Activating Factor (PAF) is involved in the cerebrovascular response to ischemia, and that its binding to platelets may change in stroke victims. The purpose of this study was to determine whether binding of PAF to platelets of stroke patients could serve as an index for determining the volume of ischemic strokes and severity of neurological presentation. Thirteen stroke patients and 21 healthy controls were studied. The neurological severity of these stroke patients was evaluated by the Scandinavian Stroke Scale. Infarct volume was assessed by planimetric measures of brain CT. PAF binding to platelets was determined by use of radiolabelled PAF. (3H)PAF binding to platelets of stroke patients was lower than in controls (149.58 ± 46.11 and 212.1 ± 10.3 receptors cell-1, respectively, p < 0.001) and was significantly correlated with infarct volume (r = -0.606, p = 0.014) and with neurological score (r = 0.527, p = 0.032). No correlation was observed between neurological score and infarct volume. The study confirms the involvement of PAF in the pathogenesis of brain ischemia and neuronal damage. It shows that PAF binding to platelets of stroke patients correlates both with the extent of neuronal damage and the associated neurological impairment, and may serve as an additional index in the assessment of stroke severity and clinical outcome of stroke victims.