"Medical research" is taken to mean actions conducted in a methodically directed manner that are intended to produce a gain in knowledge in the field of medical science. So-called "clinical trials" for the testing of drugs, vaccines and medical devices constitute an important subcategory within medical research. The testing of new surgical techniques similarly falls under the term "medical research", although there are often - as is the case in Germany - no special statutory regulations governing this type of research.

In the area of pharmaceutical trials a distinction is normally made between four methodological phases: in phase I trials a new type of substance is administered for the first time to a small number of healthy test subjects and its compatibility is studied. In Phase II studies a new substance is tested for the first time on a relatively small number of sick test patients with an eye to its effectiveness and any possible side-effects. In Phase III trials the effectiveness and safety of a new type of substance is tested on a large number of subjects. Phase IV trials are performed after licensing of a new drug in order to detect rare side-effects and unknown interactions with other drugs.