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

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