To define the determinants of anal-rectal shedding of human immunodeficiency virus (HIV) DNA and RNA, 374 HIV-seropositive homosexual men were tested. Factors independently associated with detection of anal-rectal HIV DNA included anal-rectal inflammation and detection of anal human papillomavirus DNA; predictors of HIV RNA included detection of anal-rectal HIV DNA, anal-rectal inflammation, and high plasma HIV RNA levels. The latter (>10,000 copies/mL) was the main determinant of anal-rectal HIV RNA shedding when HIV DNA (e.g., HIV-infected cells) was not detected in the anal-rectal sample. The local presence of HIV-infected cells and local inflammation were the principal determinants of HIV RNA among those with low (<10,000 copies/mL) plasma HIV RNA load. Among those with anal-rectal HIV DNA present, increased HIV RNA plasma load did not increase the risk of shedding of HIV RNA into the anal-rectal canal.