[Extract] Molecular biology is in the process of revolutionising medicine. Some people speak of "molecular medicine" as if it were a discipline akin to endocrinology or haematology, but this is not true. Not only is it untrue, it encourages an unfortunate tendency to distance one's self from the action and regard molecular medicine as someone else's game. In truth, molecular medicine is for all of us, general practitioners and specialists alike. Molecular diagnostic methods and recombinant prophylactic and therapeutic approaches now pervade every discipline of medicine and their relevance to companion animal work will continue to grow rapidly in the near future. Think of molecular biology as an increasingly useful 'toolkit' for scientists and clinicians rather than a separate scientific discipline that can be safely ignored. The good news is that clinically-relevant aspects of molecular biology and medicine are straightforward for veterinarians to grasp, as a consequence of our broad scientific education. In this article I shall not waste your time describing details of methods you are unlikely to use yourselves. Rather, I'll provide a range of companion animal examples of situations in which molecular techniques are proving valuable and I'll aim to emphasise the strengths and shortcomings of some of the described approaches. After reading this, I hope you will feel a bit better able to evaluate and critique novel veterinary molecular diagnostic and therapeutic approaches as they are developed and offered to you for purchase.