90 patients with acute stroke and a concomitant cardiac embolism source or a symptomatic high-grade stenosis of an extra-or intracranial vessel received in a mulitcenter, randomized, controlled study either Enoxaparin 1 mg/kg BW s.c. b.i.d. or i.v. heparin aPTT-adjusted daily for 8 +/- 2 days as secondary prophylaxis. There were no significant differences between the two groups regarding cerebral and systemic embolic events, bleeding complications, length of hospital stay, number of diagnostic and therapeutic measures and outcome after three months. This suggests that Enoxaparin, which is easier to administer and monitor, is a safe drug in patients with acute cerebral events.