We applaud McCarthy et al for their research addressing a critical issue in feral cat management. We concur that feral and free-roaming cats pose myriad problems for people and the environment. However, we believe that the authors overlooked several important factors when concluding that trap-vasectomy- hysterectomy-release (IVHR) "should be recommended as a humane and more effective method of decreasing population size." First, the population model used in the study does not represent a typical managed feral cat colony. Inclusion of self-imposed restraints on colony size attributable to a hypothetical carrying capacity restricts the population from reacting naturally to resources or control efforts. The model's lack of immigration and emigration restricts its application solely to small island situations. Likewise, the model does not appear to account for recapture of animals already treated in the population.