In the last decade a great effort has been devoted in animal evolutionary ecology to searching for interindividual and interspecific differences in anti-parasite resistance. Although many examples of variability in health-related traits were described in natural animal populations, our knowledge about the underlying genetic features dermining this variance is only limited. It has been shown in numerous examples in laboratory animals, domestic animals and humans that variation in the Major histocompatibility complex (MHC) is unable to explain all known genetically determined immunological variation in animals. Still MHC is so far the only gene cluster studied in ecological immunology of free-living animals. In this review we therefore map the potential importance of another group of immunity genes, the Toll-like receptors (TLRs). These innate immunity receptors belong among the most essential components of animal pathogen-recognition system and being reasonably polymorphic they might be responsible for substantial part of variation in disease-resistance in animals.