Development of new veterinary antibacterials is an important and challenging endeavor. Global recognition of antimicrobial resistance as a threat across human, animal, plant, food, and environmental sectors has increased the level of scrutiny on veterinary antibacterial use. Rigorous scientific evaluation of these products has and continues to be the underpinning of effectiveness evaluations and how hazards are identified, characterized, and ultimately used to make evidence-based and risk-based safety decisions. Some scientific factors commonly considered in the development of veterinary antibacterials include the pathogenesis and sequelae of the indicated disease, clinical and bacteriological improvement, dosage regimen (dose amount, route, duration, frequency), and antimicrobial-resistance qualitative risk assessments. Key discussion areas covered are how culture and susceptibility testing help determine if antibacterial effects are primarily responsible for clinical improvement and how pharmacokinetic and pharmacodynamic data can help predict success, aid in defining an adequate dosage regimen, and help minimize resistance emergence and spread. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.