This article examines international and European regulations on research involving prisoners for consensus, differences, and their consequences, and offers a critical evaluation of the various approaches. Agreement exists that prisoners are at risk of coercion, which might interfere with their ability to provide voluntary informed consent to research. Controversy exists about the magnitude of this risk and the consequences that should follow from this risk. Two strategies are proposed for a method of protecting prisoners that does not lead to discrimination: first, more caution to assure non-coerced consent and second, restrictions on the type of research. Most regulations stress the importance of the principle of equivalence of healthcare in places of detention as part of an efficient protection against research risks and discrimination. All the presented approaches have shortcomings. While 'over-use' of prisoners for research as compared to the general population is ethically unjustified, not granting prisoners access to studies beneficial to their own health because of over-strict regulations is equally unjustified. A middle solution should be preferred, one that grants a minimum of protection together with the lowest possible barriers. Research that does not entail a direct benefit for the individual detainee should be restricted to types of research that have a benefit for detainees as a group and that are of low risk. What will ultimately protect prisoners best, while producing the greatest benefit for them, is access to the same healthcare available to members of the community including research as a true option.