There are currently few detailed studies describing HIV-1 recombination events or the potential impact of recombination on drug resistance. We describe here the viral recombination dynamics in a drug-naive patient initially infected with a circulating recombinant form 19 (CRF19) virus containing transmitted drug resistance mutations followed by superinfection with "wild-type" subtype B virus. Single genome analysis showed replacement of the primary CRF19 virus by recombinants of the CRF19 virus and the superinfecting subtype B virus. The CRF19/B recombinant virus dominating after superinfection had lost drug resistance mutations and at no time was the superinfecting subtype B variant found to be dominant in blood plasma. Furthermore, the detection of recombinant viruses in seminal plasma indicates the potential for onward transmission of these strains.