March 2000 - Malaria ranks among the foremost health problems in tropical countries. Allowing for reverse causation, malaria is estimated to reduce GDP per capita growth rates by at least a quarter percentage point a year in many Sub-Saharan countries. McCarthy, Wolf, and Wu explore the two-sided link between malaria morbidity and GDP per capita growth. Climate significantly affects cross-country differences in malaria morbidity. Tropical location is not destiny, however: greater access to rural health care and greater income equality are associated with lower malaria morbidity. But the interpretation of this link is ambiguous: does greater income equality allow for improved anti-malaria efforts, or does malaria itself increase income inequality? Allowing for two-sided causation, McCarthy, Wolf, and Wu find a significant negative causal effect running from malaria morbidity to the growth rate of GDP per capita. In about a quarter of their sample countries, malaria is estimated to reduce GDP per capita growth by at least 0.25 percentage point a year. This paper - a product of Public Economics, Development Research Group - is part of a larger effort in the group to study the health-environment-economy nexus. This study was funded by the Bank's Research Support Budget under the research project Health, Environment, and the Economy (RPO 683-73). The authors may be contacted at fmccarthy@worldbank.org and holger.wolf@mailexcite.com.