In order for their research to be legitimate, scientists carrying out research using animals must comply with rules and regulations. The 3Rs (replacement, reduction and refinement) are one set of guidelines that help to promote the ethical use of animals for research. An important question is whether implementing the principles of the 3Rs in legal regulations, such as a Directive of the European Parliament and of the Council on the protection of animals used for scientific purposes, will increase compliance with the principles of the 3Rs in research organizations. Previous work suggests that organizational culture is just as important for directing behavior as are formalized rules and regulations. This article introduces the concepts of compliance and organizational culture and discusses their consequences on the implementation of the principles of the 3Rs.