The polymerase chain amplification reaction (PCR) is a sensitive, specific, and quantitative assay of human immunodeficiency virus type 1 (HIV-1). The assay was performed with polymerases from Escherichia coli or Thermus aquaticus (Taq). A single pair of oligonucleotide primers within the long terminal repeat (LTR) sequences were used to detect HIV-1 sequences in infected cell cultures and fresh tissues of the large majority of infected individuals. The amplified product was a faithful copy of this LTR sequence. Utilization of a subsaturating number of cycles of amplification allowed quantitation of HIV-1 DNA sequences.