A clinical investigator's brochure is a summary of the preclinical and clinical information about a drug that is about to enter clinical trials. It serves to update clinical investigators on the possible benefits, risks, and areas of uncertainty still left to be studied. The writer of the clinical investigator's brochure can create a streamlined, succinct, and easily readable document by using a format that closely parallels the research and the development history of the drug, as follows: 1) Introduction, 2) Chemistry, 3) Pharmacy, 4) Animal Pharmacology, 5) Animal Toxicology, 6) Animal Pharmacokinetics, 7) Clinical Experience, 8) Possible Risks and Precautions, and 9) Bibliography. In this article, the author explains what information is needed in each of these sections and suggests ways to avoid redundancy.