Dispersed polymer nanocapsules can serve as nano-sized drug carriers to achieve controlled release as well as efficient drug targeting. Equipped with site-specific markers or guided by magnetic forces, they may transport an active ingredient to a specific tissue, hereby allowing for lower dosages and a significant reduction of side effects. In that sense, nanocapsules could represent the “magic bullet” for a pharmaceutical therapy. In principal, nanocapsules can be prepared by four different approaches: interfacial polymerization, interfacial precipitation, interfacial deposition, and self assembly procedures. All these procedures offer their individual advantages and disadvantages when it comes to the design of optimized drug carrier systems. The most important capsule parameters such as capsule radius distribution, the capsule surface, the thickness and, above all, the permeability of the capsule membrane and its thermal or chemical decomposition, can be controlled within wide margins. The success of the encapsulation process as well as the permeability of the capsule membranes is efficiently determined with adapted methods of nuclear magnetic resonance spectroscopy (NMR). Examples for optimized capsule systems are shown which represent present developments used for a magic bullet approach. They include the transfer of genes, the application for tumor treatment, and the function as artificial oxygen carrier for artificial blood replacement. In combination with efficient preparation procedures, nanocapsule dispersions allow for new and promising approaches in many kinds of pharmaceutical therapies.