Improving the means of drug delivery has become an important field of pharmaceutical research. The development of safe and advanced vectors for gene therapy and other novel therapies will allow for targeted delivery of pharmaceutically active agents and carries promise to improve therapies both through increased efficiency (e.g. improved cellular uptake of the active drug) as well as lower toxicity (e.g. through targeted delivery only to the cells requiring treatment) for a large number of pharmaceutical agents. Here we are reviewing the nascent field using live bacteria as vectors for therapeutic and preventive agents in a wide range of areas, from vaccine purposes to gene therapy and delivery of therapeutic RNA interference. This review focuses particularly on the use of E. coli derived strains for therapeutic delivery.