The polymerase chain reaction (PCR) has been the most promising test for HIV-1 early diagnosis in infants suspected of perinatal transmission. The first and second reactions of the amplification in 41 infants (under 18 months old) suspected of HIV-1 perinatal infection, were standardized and carried out in the present study. The first and the second PCR were carried out with the sets of primers JA4-JA7, JA9-JA12, JA13-JA16, and JA17-JA20 for the first reaction of amplification (outer primers) and JA5-JA6, JA10-JA11, JA14-JA15, and JA18-JA19 for the second reaction of amplification (inner primers), resulting in amplification of 131, 341, 172, and 129 pb, respectively. From 41 patients analysed, 12 patients presented positive to HIV-1 infection by PCR. The gag, env (region 1), and pol regions presented a greater sensitivity. The first and the second reactions of the amplification were performed with the same concentration of MgCl2 for all sets of primers. The results agree with several studies that affirm that the PCR is the indicated method for HIV-1 early diagnosis in infants suspected of perinatal infection.50107-13