Book excerpt: Medical Eligibility Criteria for Contraceptive Use reviews the medical eligibility criteria for use of contraception, offering guidance on the safety and use of different methods for women and men with specific characteristics or known medical conditions. The recommendations are based on systematic reviews of available clinical and epidemiological research. It is a companion guideline to Selected Practice Recommendations for Contraceptive Use. Together, these documents are intended to be used by policy-makers, program managers, and the scientific community to support national programs in the preparation of service delivery guidelines. The fourth edition of this useful resource supersedes previous editions, and has been fully updated and expanded. It includes over 86 new recommendations and 165 updates to recommendations in the previous edition. Guidance for populations with special needs is now provided, and a new annex details evidence on drug interactions from concomitant use of antiretroviral therapies and hormonal contraceptives. To assist users familiar with the third edition, new and updated recommendations are highlighted. Everyone involved in providing family planning services and contraception should have the fourth edition of Medical Eligibility Criteria for Contraceptive Use at hand.