Twenty CT proven patients of thrombotic stroke who were non-diabetic, non-hypertensive and non-hyperlipidemic were evaluated in acute phase (within 7 days of onset of neurological deficit) for platelet count and spontaneous platelet norepinephrine (NE) efflux, measured as the fraction (of initial total content) of 3H-NE released from platelets in 30 and 60 min. NE efflux was significantly greater (P less than 0.001) in stroke patients (34.09 +/- 4.92% at 30 min and 50.45 +/- 7.1% at 60 min) as compared to controls (23.27 +/- 4.16% at 30 min and 39.49 +/- 3.27% at 60 min). This excessive efflux may result in increased concentrations of NE in local plasma, which by causing enhanced platelet aggregation and damage to vascular endothelium and vasospasm, may contribute towards the development and progression of cerebral thrombosis.