T-lymphocytes, dendritic cells and macrophages are the target cells for HIV. The infected macrophages are considered as reservoirs for spreading the virus. Treatment of HIV infection therefore must reach these cells in addition to the organs like brain, liver and bone marrow. Lectin receptors, which act as molecular targets for sugar molecules, are found on the surface of these cells of the phagocytic system. The purpose of the present study is to investigate the targeting potential and anti HIV activity of lamivudine (3TC) loaded mannosylated fifth generation Poly (propyleneimine) dendrimers (MPPI). The entrapment efficiency of 3TC loaded MPPI and 5th generation poly(propyleneimine) dendrimer (PPI) were found to be 43.27+/-0.13% and 35.69+/-0.2% respectively. The in vitro drug release profile shows that while PPI releases the drug by 24 h, the MPPI slows down and hence prolongs the release up to 144 h (96.89+/-1.8% in case of MPPI). The results of in vitro ligand agglutination assay indicated that even after conjugation with PPI, mannose displayed binding specificity towards Con A. The subtoxic concentrations of free 3TC, blank PPI, blank MPPI, drug loaded PPI and drug loaded MPPI, determined on MT2 cells, were found to be 0.625, 0.039, 0.156, 0.039 and 0.156 nM/ml respectively. Significant increase in cellular uptake of 3TC was observed when MPPI was used, which was 21 and 8.3 times higher than that of free drug (p<0.001) and PPI (p<0.001) at 48 h respectively. Antiretroviral activity was determined using MT2 cell lines by estimating p24 antigen by ELISA. 3TC loaded PPI and MPPI formulations were found to possess higher anti-HIV activity at a concentration as low as 0.019 nM/ml, as compared to that of free drug, which was found to be extremely significant (p<0.001). The significantly higher anti-HIV activity of PPI and MPPI is due to the enhanced cellular uptake of 3TC in formulation as compared to that of free drug Results suggest that the proposed carrier hold potential to increase the efficacy and reduce the toxicity of antiretroviral therapy.