Surgery in laboratory animals is an orphan field of veterinary medicine. Nevertheless, it is of the utmost importance in the development of new drugs, including their pharmacokinetic/pharmacodynamic properties, their toxicity, and their efficacy. It is also an inherent part of animal studies for the evaluation of medical devices for regulatory submission, thus improving public health. Application of the 3Rs (Replacement, Reduction, Refinement of animal use) allows surgeons to ensure that animal welfare is optimal and that unnecessary suffering is reduced to an absolute minimum while still achieving scientific objectives. In addition, surgery as a field has been subjected to stringent reviews by both ethical committees and peer review of scientific research, which has obliged us to greatly refine our surgical techniques, resulting in improved and more reproducible outcomes. This chapter will discuss the implementation of good practice in aseptic technique for surgery in laboratory animals including small (mouse, rat) and large animal models (rabbit, sheep, pig, and non-human primates).