This paper provides an in-depth understanding of the concept of biological control (biocontrol). In doing so, it interprets important biological principles of control methodology, and it intercalates these discussions with analysis of the biological backlashes and other ecological interactions that may be created whenever vertebrate "pests" are control by biological means. The concept "balance of nature" is explained, noting that only in the most remote area is human impact on the environment not present. The term "biological control" is defined as an attempt to reduce the population density of a pest species (e.g., increase mortality, reduce natality, or cause significant emigration) either by increasing predation, changing habitat conditions, introducing or stimulating epizootics, or by use of antifertility agents. The dynamics of vertebrate population are examined in detail. Detail discussion in provided on predators (both native and introduced), habitat modification, diseases, and chemosterilants, in regard to both mammals and birds. The greatest likelihood for effective application of biological control of existing pestiferous vertebrate populations is by means of integrated control (i.e., where biological control is done concomitantly with an initial population reduction by some conventional control method). An extensive literature review is provided.