In the present study HIV-1 quasispecies were analysed in Langerhans cells derived from eight spli-thickness skin patches obtained from clinically normal skin taken soon after autopsy from an AIDS patients (coded RI). RI was an Italian drug user who had been HIV-1 Ab positive from 1986. It is not possible to formally conclude that patient RI was infected twice. RI could have been infected once by blood from a doubly infected individual. However double infection clearly must have occurred at some point. A number of independent experimental studies and phylogenetic analysis provides strong evidence for double infection. That detection is so infrequent might reflect the fact that a second infection most probably would occur in the face of HIV-specific immune response, so restricting viral replication.