In the past decade, the pharmaceutical industry has realized the increasing significance of impacting the early phase hit-to-lead development in the drug discovery process. In particular, knowledge-based approaches emerged and evolved to address a multitude of issues such as absorption, distribution, metabolism and excretion (ADME), potency, toxicity and overall drugability. Each of these approaches seeks to bring together all relevant pieces of information and create a knowledge-oriented process to deploy such information in drug discovery. This review focuses on work relating to drugability, which aims at obtaining hits (or leads) that have enhanced likelihoods of leading to successful clinical candidates by medicinal chemistry efforts. The period covered in this review is from 1997 (since the publication of Lipinski's rule of 5) to March 2002.