Reversibly stabilized DNA nanoparticles (rSDN) were prepared by coating reducible polycation/DNA complexes with multivalent N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers. RGD-targeted rSDN were formulated by linking cyclic c(RGDyK) to the surface layer of rSDN. Cellular uptake in B16F10 mouse melanoma cells, human umbilical vein endothelial cells (HUVEC), and THLE immortalized hepatic cells was quantified by real-time PCR. RGD-targeted rSDN exhibited approximately twofold higher cell uptake in integrin-positive cells: B16F10 and HUVEC compared to THLE cells with low integrin content. RGD-targeting mediated increased transfection activity in B16F10 cells but not in THLE cells. Overall, the studies show that rSDN can be effectively targeted with RGD while exhibiting reduced nonspecific cell interactions and favorable stability. As such, these gene delivery vectors have the potential to permit targeting therapeutic genes to tumors by systemic delivery. In addition, the study shows that real-time PCR could be used effectively for the quantification of cellular uptake of gene delivery vectors.