Intracellular targeting of ampicillin by means of polyisohexylcyanoacrylate (PIHCA) nanoparticles was studied in murine peritoneal macrophages infected with Salmonella typhimurium. The intracellular distribution of actively endocytosed nanoparticles was visualized by transmission electron microscopy and confocal microscopy. Nanoparticles were either isolated or closely associated with bacteria within phagosomes or phagolysosomes. Thus the potential of ampicillin-loaded nanoparticles.in targeting of intracellular bacteria is demonstrated. Consequently, ampicillin, which usually penetrates into cells at a low level, is directly carried in, when loaded on nanoparticles, and brought into contact with intracellular bacteria.