The U.S. Food and Drug Administration (FDA) is in the process of preparing a draft Guidance for Industry document on the statistical aspects of carcinogenicity studies of pharmaceuticals for public comment. The purpose of the document is to provide statistical guidance for the design of carcinogenicity experiments, methods of statistical analysis of study data, interpretation of study results, presentation of data and results in reports, and submission of electronic study data. This article covers the genesis of the guidance document and some statistical methods in study design, data analysis, and interpretation of results included in the draft FDA guidance document.