Tissue engineering studies are complex in nature and involve many stages of testing before an experimental construct is ripe for human clinical trials. Biocompatibility questions, toxicological problems, pharmacological aspects, safety issues and proof of the principle itself represent but a few of the concerns that must be addressed. This contribution deals with the different types of animal experiment that are usually undertaken in tissue engineering studies. During the initial phase, small animal models are used to screen all potential components of the proposed construct, such as matrix, cells and signalling substances. In the second, the principle itself is put to the test using an appropriate defect model in a suitable animal species. Careful consideration of these latter two aspects is of paramount importance, many factors having to be considered and special requirements satisfied for meaningful experimentation. Finally, clinically relevant models are set up in animals to furnish basic information respecting the construct's suitability and ripeness for testing in human clinical trials.