Abstract: Aim To describe a simple and efficacious monitoring system for patients presenting with severe dengue with severe plasma leakage. Method: We reviewed sixty-one out of 110 records of patients presenting with dengue in August and September of 1999 at the Hospital Tony Facio, Limón province, Costa Rica. Results: Dengue virus 3 was the cause of the epidemic. Thirty one (51%) patients presented with warning sings, and thirty (49%) had severe dengue with severe plasma leakage. Those patients presenting with hypotension (low mean arterial blood pressure) were treated with an intravenous polyelectrolyte solution in order to maintain the mean arterial pressure between the lower and mean range. When the mean arterial pressure presented a tendency to rise over the normal range, the infusion was withdrawn. The hematocrit was not the parameter used to monitor the treatment of the patients. There were no deaths. Conclusions: Monitoring the mean arterial blood pressure instead of the hematocrit values in patients with severe dengue with severe plasma leakage represents an easier and more efficacious way of treating this patient population.