Our esteemed colleague Dr. Michael Vlassoff passed away suddenly in November 2016. Dr. Vlassoff joined the Guttmacher Institute, where he was a Senior Research Scientist, in 2008; he served as a consultant to the Institute from 2003 to 2008. He made important contributions to the field of sexual and reproductive health research and he will be greatly missed. Dr. Vlassoff was a population economist with 25 years of experience in the United Nations in the areas of modeling population-development interrelationships, economic aspects of fertility in developing countries and the costing of sexual and reproductive health services. Dr. Vlassoff’s work with the Institute concentrated on analysis of the cost of abortion-related morbidity and mortality. He had recently undertaken pioneering studies on the health systems cost of unsafe abortion and contributed to the pilot study on the cost of unsafe abortion. Dr. Vlassoff obtained a Ph.D. in economics from the University of Pune.