Data extracted from health records are commonly used in studies to address a variety of questions raised by health researchers. However, concern about the reliability and validity of such data generally is limited to an assessment of interrater reliability. Less attention has been paid to the reliability of the health record itself, and to the validity of both the health record and the data extracted from it. This article reviews the distinctions and overlaps among these types of reliability and validity and the factors that influence the validity and reliability of research data obtained from health records. Recommendations to investigators who use health record data in their research projects are offered.