Interspecific killing among mammalian carnivores is common and accounts for up to 68% of known mortalities in some species. Interactions can be symmetrical or asymmetrical, with larger species often killing both adults and juveniles of smaller species. Group-living carnivores kill larger victims than solitary ones, and such interactions are more common when food is scarce. Victim species may alter space use, activity patterns, and group formation in response to killers. Interspecific killing can lead to population reduction or extinction, and may influence prey populations. It has important implications for conservation and management of carnivores and their prey. Interspecific killing is widespread among mammalian carnivores, with 97 different pairwise interactions involving 54 victim and 27 killer species. Canids, mustelids, and felids are most involved. The red fox is the most common victim, while Panthera and Lynx are the most common killers. Smaller species are more likely to be killed by larger ones, and grouping plays a role in the outcome of interactions. Group-living carnivores can kill victims up to 12 times their own body mass. Some carnivores consume their victims, with 10 of 21 killer species eating them. Availability of alternative prey influences both killing and consumption. Interspecific killing can have direct effects on victim populations, with mortality rates ranging from 43% to 68%. It can lead to population declines or extinctions, and may limit the density of certain species. Indirect effects include shifts in space use, temporal segregation, and group formation, which help avoid predation. Interspecific killing can also influence prey populations through mesopredator release, where the removal of top predators allows smaller predators to increase, potentially affecting prey. Conservation efforts must consider these interactions, as some endangered species are negatively impacted by larger carnivores. Protecting top carnivores can help control smaller predators and benefit prey populations. Interspecific killing is common in carnivore communities, but its ecological and behavioral factors are poorly understood. Further study is needed to determine how life-history traits and productivity affect interaction intensity and victim consumption. Quantitative data on carnivore and prey populations is essential for understanding the ecological consequences of interspecific killing. Natural experiments and long-term monitoring are important for inferring these effects.Interspecific killing among mammalian carnivores is common and accounts for up to 68% of known mortalities in some species. Interactions can be symmetrical or asymmetrical, with larger species often killing both adults and juveniles of smaller species. Group-living carnivores kill larger victims than solitary ones, and such interactions are more common when food is scarce. Victim species may alter space use, activity patterns, and group formation in response to killers. Interspecific killing can lead to population reduction or extinction, and may influence prey populations. It has important implications for conservation and management of carnivores and their prey. Interspecific killing is widespread among mammalian carnivores, with 97 different pairwise interactions involving 54 victim and 27 killer species. Canids, mustelids, and felids are most involved. The red fox is the most common victim, while Panthera and Lynx are the most common killers. Smaller species are more likely to be killed by larger ones, and grouping plays a role in the outcome of interactions. Group-living carnivores can kill victims up to 12 times their own body mass. Some carnivores consume their victims, with 10 of 21 killer species eating them. Availability of alternative prey influences both killing and consumption. Interspecific killing can have direct effects on victim populations, with mortality rates ranging from 43% to 68%. It can lead to population declines or extinctions, and may limit the density of certain species. Indirect effects include shifts in space use, temporal segregation, and group formation, which help avoid predation. Interspecific killing can also influence prey populations through mesopredator release, where the removal of top predators allows smaller predators to increase, potentially affecting prey. Conservation efforts must consider these interactions, as some endangered species are negatively impacted by larger carnivores. Protecting top carnivores can help control smaller predators and benefit prey populations. Interspecific killing is common in carnivore communities, but its ecological and behavioral factors are poorly understood. Further study is needed to determine how life-history traits and productivity affect interaction intensity and victim consumption. Quantitative data on carnivore and prey populations is essential for understanding the ecological consequences of interspecific killing. Natural experiments and long-term monitoring are important for inferring these effects.