In research funded by NIDA and the Fogarty International Center (FIC), Jasmin Vassileva, Ph.D., University of Chicago, is investigating the impact of heroin on neurocognitive function and HIV transmission in Bulgaria. Why Bulgaria? In Chicago, up to 80% of heroin users also use cocaine, making it difficult to isolate the effects of a single drug. In contrast, Bulgarian heroin users are more likely to use only that drug. In addition, both heroin addiction and HIV are major public health problems and research is scarce in the country where Dr. Vassileva was born. Dr.