Much of clinical and hospital epidemiology involves the identification and enumeration of cases or the comparison of case frequencies between two or more groups of interest. Because both of these activities involve the use of statistics, it is important to pay careful attention to biostatistical issues involved in the collection and the analysis of such data.

In this article, the first in a series of biostatistical papers, we discuss some general issues that are important in the design, analysis, and interpretation of clinical epidemiologic data. Subsequent papers in this series will deal with specific methods of analysis, examples of these methods of analysis, and limitations and interpretations of the methods.