Sponsors of new drug applications (NDAs) confront a host of uncertainties, one of the more vexing of which is negotiating the differing and inconsistent policies and standards among the various US Food and Drug Administration (FDA) drug review divisions. The FDA faces many challenges as well, internal and external, that confound its efforts to provide a consistent and timely review process. In this article, we examine various input factors, such as the number of regulatory filings, that contribute to fluctuations in the annual FDA workload, as well as output factors, such as NDA approval times, that are often viewed by sponsors as measures of the FDA's performance. Interdivisional differences at the FDA, in both input and output factors as well as other process-related factors, such as issuance of complete response letters, division staff levels, and quality of the sponsor's application, are considered in light of their contribution to the vagaries of the sponsors' experiences with the regulatory process.