In recent decades, spay or neuter of dogs, including early-age spay-neuter, has become a common practice in the United States, intended primarily to reduce overpopulation and therefore relinquishment of dogs to animal shelters and humane societies. Neutering dogs prior to adoption is even, in some localities, a legal requirement. However, recent research has called into question the common wisdom of mandatory and indiscriminate spay-neuter. An important welfare issue is that for some canine breeds, neutering is associated with heightened levels of musculoskeletal disorders and/or certain cancers, while for others no adverse effects of neuter status on diseases are evident. Adverse consequences of early neutering can be particularly troubling for the breeds most often used in working or assistance roles, shortening the working lives of these extensively trained dogs, e.g., Golden Retrievers, Labrador Retrievers, and German Shepherds. It must also be considered that, in many countries outside of the United States, dog populations are not routinely sterilized and, in some cases, maintain low rates of dog relinquishment. In other cases, where street dog populations are prevalent, results of long-term sterilization program are mixed as to their success in preventing or reducing street dog populations. It is clear that reproduction is not the sole cause of dog relinquishment, and that an outsized focus on sterilization can inhibit efforts to protect animals and, in some cases, be harmful to them. These issues raise questions regarding legal implications, adoption, and methods of controlling reproduction. This Research Topic seeks to provide a scholarly forum addressing the numerous contexts and complexities, including cultural and legal issues related to spay and neuter of dogs. collapse