It has become widely accepted that we may be biologically “prepared” to associate fear more easily with some stimuli (e.g., heights) than with other stimuli (e.g., electric outlets). The current literature on the topic of the genetics of fears and phobias is surveyed with an eye toward answering the question “What might be heritable?” For ordinary fears among the general population, heredity appears to contribute mainly to a trait of general fearfulness and may be a major reason for the strong intercorrelation among different fears. Surprisingly, the available evidence suggests little environmental transmission from parent to offspring, although adoption data have yet to be reported on this issue. Although the results of two small twin series are consistent with some genetic influence on clinically significant phobias, it is still not clear what might be genetically transmitted in these disorders. There is a strong possibility that phobic disorders may be genetically heterogeneous.