Abstract BACKGROUND: Progressive stroke (PS) and Crescendo Transient Ischemic Attacks (CTIA) is a generally accepted although unproven, indication for urgent intravenous anticoagulation therapy. METHODS: Consecutive patients with PS and CTIA admitted in Ghaem hospital, Mashhad during 2007 - 2008 enrolled in a prospective clinical study. PS and CTIA patients underwent intravenous heparin therapy with 1000 units per hour without a bolus dose at least for 3 days. PS and CTIA patients who had a contraindication for intravenous hepain therapy, received 80 mg Aspirin per day. Early clinical course including improvement, stabilization, deterioration and development of residual stroke was evaluated in two therapeutic groups of PS and CTIA patients. RESULTS: 170 PS patients (103 males, 67 females) with mean age of 60.4 ± 12.3 years and 88 CTIA patients (50 males, 38 females) with mean age of 60.1 ± 6.8 years were assessed. 141 PS and 64 CTIA patients received short period intravenous heparinization. Distribution of subtypes of early clinical course between two therapeutic groups of PS and CTIA patients, was significantly different; X2 = 10.487, df = 2, p = 0.005 and X2 = 6.72, df = 2, p = 0.035 respectively. Distribution of residual stroke in two therapeutic groups of PS and CTIA patients,was not significantly different; X2 = 1.443, df = 1, p = 0.23, OR = 0.557 (0.212-1.462) and X2 = 1.01, df = 1, p = 0.315, OR = 0.617 (0.24-1.587) respectively. CONCLUSION: PS and CTIA patients who underwent short period intravenous heparin therapy have significantly more probability of improvement and less probability of deterioration in their early clinical course than PS and CTIA patients who received Aspirin therapy. Keywords: Progressive Stroke (PS) Crescendo TransientIschemic Attacks (CTIA), Intravenous anticoagulation therapy, Heparin therapy.