Background: Early diagnosis of perinatally acquired HIV-infection is based on either direct HIV detection-by means of viral culture and/or PCR-or anti-HIV antibody detection. However, due to the passive, transplacental passage of maternal immunoglobulin G, antibody detection is nor reliable until 15-18 months of age. In this regard, clonotypic analysis of specific antibodies performed by isoelectricfocusing and reverse blotting (IEF-RB) can be very helpful, as it recognizes possibly different patterns between mother and infant. Objectives: We used IEF-RB in order to analyze the kinetics of development of anti-HIV antibodies in infants born to seropositive mothers. Study design: Sera from ten mother/infant pairs tall mothers were HIV-infected) were retrospectively analyzed in order to detect different patterns, between mother and infant, in anti-gp120 V-3-loop clonotype. Results: We diagnosed the real HIV status of the examined infants no later than month 6 and in one case as early as month 2. Conclusions: Considering the small size of sample number, these data are preliminary and should be confirmed by larger scale studies. However, they show IEF-RB, when applied to infants born to seropositive mothers, may be useful in evaluating the infants' dynamics of anti-HIV humoral immune response. (C) 1998 Elsevier Science B.V. All rights reserved.