My research concerns the development of statistical methods for missing data, causal inference, and sensitivity analysis, with focus on applications in HIV/AIDS. As part of my collaborations, I serve as Co-Director of the Biostatistics Program for AMPATH, an international consortium of universities in the US, Canada and Kenya focused on treatment and prevention of HIV in Kenya and co-Director of the Biostatistics Core for the Providence-Boston Center for AIDS Research. My basic and collaborative research is funded by the NIH and NSF.