This article reviews most systems and approaches for delivery of protein drugs and therapeutic genes into the body. Issues in drug delivery are becoming more important as more potent and specific drugs become available, with knowledge about diseases available from the human genome project. To achieve optimal therapeutic efficacy, drug delivery systems should be customized and very innovative. Novel systems are often nanosized, prepared with the use of specific excipients, and they also have multifaceted advantages in drug delivery. These systems in general can be used to provide targeted (cellular/tissue) delivery of drugs, to improve oral bioavailability, to sustain drug/gene effect at target place, and to improve the stability of therapeutics agents against enzymatic degradation, especially of protein, pep­tide and nucleic acid drugs. Vectors for gene delivery can be divided into two major groups: viral and nonviral. Due to several limitations of viral vectors, nonviral vectors attract more attention; they consist of a carrier with cationic character that is able to associate with the negatively charged DNA molecule. Formation of this complex protects DNA against dena­turation and enables its entry into cells. For specific processes that must take place, such as cell recognition, endocytosis, cytosolic trafficking, endosomal escape, dissociation of the com­plex, efficient nuclear uptake and gene expression, several specific molecules are attached to gene delivery devices enabling targeting, fusion with the membrane and changes in the microenviroment, or other ways of affecting cellular function for successful transgenic expres­sion. Combinations of viral and nonviral components are hybrid vectors, which are safer than viral vectors and more efficient than nonviral ones.