For early cancer diagnosis and treatment, a nanocarrier system is designed and developed with key components uniquely structured at nanoscale according to medical requirements. For imaging, quantum dots with emissions in the near-infrared range (∼800 nm) are conjugated onto the surface of a nanocomposite consisting of a spherical polystyrene matrix (∼150 nm) and the internally embedded, high fraction of superparamagnetic Fe(3)O(4) nanoparticles (∼10 nm). For drug storage, the chemotherapeutic agent paclitaxel (PTX) is loaded onto the surfaces of these composite multifunctional nanocarriers by using a layer of biodegradable poly(lactic-co-glycolic acid) (PLGA). A cell-based cytotoxicity assay is employed to verify successful loading of pharmacologically active drug. Cell viability of human, metastatic PC3mm2 prostate cancer cells is assessed in the presence and absence of various multifunctional nanocarrier populations using the MTT assay. PTX-loaded composite nanocarriers are synthesized by conjugating anti-prostate specific membrane antigen (anti-PSMA) for targeting. Specific detection studies of anti-PSMA-conjugated nanocarrier binding activity in LNCaP prostate cancer cells are carried out. LNCaP cells are targeted successfully in vitro by the conjugation of anti-PSMA on the nanocarrier surfaces. To further explore targeting, the nanocarriers conjugated with anti-PSMA are intravenously injected into tumor-bearing nude mice. Substantial differences in fluorescent signals are observed ex vivo between tumor regions treated with the targeted nanocarrier system and the nontargeted nanocarrier system, indicating considerable targeting effects due to anti-PSMA functionalization of the nanocarriers.