This paper presents a design of a health care monitoring system based on wireless sensor networks (WSN) which is capable of collecting, retrieving, storing and analysing the vital signs of the patient. Vital signs such as body temperature, blood pressure, pulse rate and respiratory rate are monitored. To manage these sensors and for collecting and storing data in a database, a Multi Agent System (MAS) is used. The dynamic nature and mobility of the agents make them suitable for maintaining these sensors in the WSN. The proposed MAS consists of four agents namely Admin agent, Control agent, Query agent and Data agent. Admin agent plays the role of invoking and terminating other agents. Control agent is responsible for storing the data sensed by the sensors into the database. Data agent performs data reduction which is achieved using Epsilon approximation. The use of Data agent in the proposed scheme reduces data traffic and the requirement of secondary storage space. Query agent is responsible for providing l sign details. The proposed agent based system has been implemented using Java language in JADE environment and the results are validated. © 2013 The Authors. Published by Elsevier B.V.