The efficiency and duration of transmissibilty of HIV seems to be high
ly variable and dependent on a number of factors related to both the d
onor and the recipient as well as characteristics intrinsic to the vir
us itself. Some of the factors likely to be important in sexual transm
ission of HIV include stage of disease, antiretroviral therapy, and co
ncomitant systemic or mucosal infections, including sexually transmitt
ed diseases. This paper describes recent work from our group in each o
f these areas.