Dr Gray has expertise in reproductive health including HIV and STD control, maternal and child health, family planning, cervical cancer screening, determinants of HIV/STD risk. He was also involved in several cohort studies and randomized trials of HIV prevention. He is a co-principal investigator of the Rakai Health Sciences Program in Uganda, and principal investigator on the NIAID-funded "Rakai Trial of Male Circumcision for HIV Prevention" and post-trial surveillance studies. These trials showed that male circumcision reduced HIV, HSV-2 and HPVI in men, and vaginal infections in female sexual partners. In addition to his research with the Rakai Program, Dr. Gray has been principal investigator on numerous international epidemiological studies of reproductive and prenatal health.