Langerhans cells (LC) are the only resident epidermal cells expressing the CD4 antigen and they can be infected by HIV-1, as demonstrated by the identification of HIV-1 DNA and mRNA in LC from seropositive patients. The aim of the present study was to evaluate the presence and relative abundance of integrated and circular forms of HIV-1 DNA in purified epidermal LC obtained from normal skin of 6 AIDS patients. Total viral load was quantified using a competitive PCR system with gag primers and a competitor plasmid DNA with a modified sequence. 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. HIV-1 DNA was found in purified LC from all patients examined, with copy number ranging from 153 to 9360/10 5 LC. Integrated provirus was detected in LC of the 2 patients presenting the highest viral load. However, in all cases the great majority of HIV-1 DNA species found appeared to be of the 1-LTR and 2-LTR type. The preponderance of unintegrated forms of viral DNA in infected LC suggests that superinfection of LC occurs in AIDS patients and raises the question of the possible role of these extrachromosomal forms in supporting HIV replication in LC.