The kinetics of copying of poly(A) . (dT),, poly(A) . (U),, poly(dA) . (dT), and poly(A) . (dT),-U by reverse transcriptase of human immunodeficiency virus-1 (HIV-1) has been studied and the binding affinity of the enzyme, for template or primer, determined. Short oligonucleotides and dTTP served as primers in the HIV-1 reverse-transcriptase-dependent DNA synthesis. K , and V,,, were measured as functions of the primer chain length; the logarithm of the values of both K , and V,,, increased linearly up to 10. For longer primers (n = 11 to n = 24) the increase of those values changes very little. The enhanced affinity of the primers, (dT), or (U), due to the formation of one complementary pair, A . dT, dA . dT, A . U was estimated as a factor of 2. A specific property of HIV-1 reverse transcriptase compared with other DNA polymerases (procaryotes, eucaryotes, other retroviruses and archaebacteria) was its higher affinity to riboprimers as compared to deoxyriboprimers.Relative initial rates when copying poly(A) or poly(dA) templates using different primers and various conditions were compared ; the optimal temperature for the reaction of polymerization with poly(A) or poly(dA) templates and (U),,, (dT),, or (dT),-U primers was determined. The maximal activity of the enzyme in the case of poly(A) and decanucleotide primers was found at temperatures between 27 -31 "C. An increase in the primer length results in the stabilization of the template . primer duplex complexed to the enzyme, thus increasing to more than 40°C the optimal temperature of polymerization. The activation energy (E,) values of the polymerization reaction for different template . primer complexes were evaluated.Recently, the mechanism of binding and elongation of homopolymers (dT),, (dA),, (dG),, (dC),, (U), and (A)" in the case of human DNA polymerase a [l -51, Escherichia coli DNA polymerase I and its Klenow fragment [l, 2, 6 -91 and DNA polymerases from archaebacteria [lo, 111 has been studied. The dependence of the K , values on the structure and length of different hetero-oligomers in the polymerization reaction catalyzed by DNA polymerase I (Klenow fragment) was determined [8]. It has also been shown that dNMP, NMP and dNTP were the minimal primers of procaryotic, eucaryotic and archaebacterial DNA polymerases [l -3, 5 -