Background and objectives: In Intensive Care Units, the amount of data to be processed for patients care, the turn over of the patients, the necessity for reliability and for review processes indicate the use of Patient Data Management Systems (PDMS) and electronic health records (EHR). To respond to the needs of an Intensive Care Unit and not to be locked with proprietary software, we developed a PDMS and EHR based on open source software and components.Methods: The software was designed as a client–server architecture running on the Linux operating system and powered by the PostgreSQL data base system. The client software was developed in C using GTK interface library. The application offers to the users the following functions: medical notes captures, observations and treatments, nursing charts with administration of medications, scoring systems for classification, and possibilities to encode medical activities for billing processes. Results: Since his deployment in February 2004, the PDMS was used to care more than three thousands patients with the expected software reliability and facilitated data management and review processes. Communications with other medical software were not developed from the start, and are realized by the use of the Mirth HL7 communication engine. Further upgrade of the system will include multi-platform support, use of typed language with static analysis, and configurable interface. Conclusion: The developed system based on open source software components was able to respond to the medical needs of the local ICU environment. The use of OSS for development allowed us to customize the software to the preexisting organization and contributed to the acceptability of the whole system.