A letter of recommendation is a statement of support for a person that has been requested by some individual or organization. In physiology, the purpose of the letter may be to support admission to an academic program, funding of a fellowship grant proposal, consideration for a trainee position in a research laboratory, an award from a professional society, or an application for a job. The goal of the letter should be to provide personalized insight into the suitability of the candidate for the position or award that cannot be easily obtained from other materials in an application or nomination process. Despite the importance of writing effective letters of recommendation, most physiologists receive no formal training in this requisite professional skill. In this Perspective, I first discuss the responsibilities and challenges of writing letters of recommendation, for whom you should consider writing a letter, the pros and cons of asking the candidate to create an initial draft, and the information required for you to write a letter. I then describe a helpful structure to follow when writing a letter of recommendation, including the opening paragraph (introduction), main body, and summary sections. Next, I share 10 insider tips for writing effective letters of recommendation. I complete the commentary by discussing special circumstances, including writing letters for solid but not highly ranking candidates and acting as a "substitute" for a primary mentor. It is hoped that this perspective will provide guidance for early career physiologists in this essential skill of the profession.
