Abstract. The use of nanoscale biomaterials as drug delivery systems has been exponentially growing in the recent years. Various functionalbiocompatible drug nanocarriers were designed in order to avoid some problems like low solubility, low bioavailability, and extended biotransformation etc. Among the carriers, mesoporous silica materials and polymeric nanoparticles emerged as a promising candidates that can deliver a variety of drug molecules in a controllable and sustainable manner.  However, the possible hazard of nanoparticles on human health is still far from well established. This review aims to give a short summary of the recent uses and toxicity studies of two types of nanoparticles proposed as drug-delivery carriers – polymeric micelles and mesoporous silica nanoparticles.