To realize the benefits of electronic health records, electronic health record information needs to be shared seamlessly and meaningfully. Clinical terminology systems, one of the current semantic interoperability solutions, were reviewed in this article. Definition, types, brief history, and examples of clinical terminologieswere introduced along with phases of clinical terminology use and issues on clinical terminology use in electronic health records. Other attempts to standardize the capture, representation and communication of clinical data were also discussed briefly with future needs.