Langerhans cells (LC) are the only resident epidermal cells expressing CD4 antigen and they can be infected by HIV-1, as demonstrated by the identification of HIV-1 DNA and mRNA in purified LC from seropositive patients. The aim of the present study was to evaluate the presence and relative abundance of integrated and circular HIV-1 DNA forms in purified epidermal LC obtained from normal skin of 6 AIDS patients. Integrated HIV-1 DNA was assessed by PCR amplification of proviral sequences circularized in vitro after digestion of LC genomic DNA. The 1-long terminal repeat (1-LTR) and 2-LTR circles were detected by semiquantitative PCR analysis using primers which selectively amplify each form. Total viral load in purified LC was quantified using a competitive PCR system with gag primers and a competitor plasmid DNA with a modified sequence. HIV-1 DNA was found in purified LC from all 6 AIDS patients examined; copy number ranged from 153 to 936010 5 LC. Although the great majority of HIV-1 DNA species in LC appeared to be of the 1-LTR and 2-LTR type, integrated provirus was also detected, confirming that infection of this cell type by HIV can be productive. On the other hand, the preponderance of unintegrated forms of viral DNA in HIV-infected LC suggests that superinfection of LC occurs in AIDS patients.