Neuroticism is a personality trait, while generalized anxiety disorder is a psychiatric diagnosis. Common features, e.g., irritability and worrying, suggest some overlap. To explore the depth of this commonality, Hettema et al. (p. 1581) contrasted the extent of genetic and environmental sources of neuroticism and broadly defined generalized anxiety disorder. Twins in 3,101 male-male, female-female, and male-female monozygotic and dizygotic pairs completed a neuroticism questionnaire and psychiatric interview. Statistical modeling indicated that the genetic factors underlying neuroticism are nearly indistinguishable from those for generalized anxiety disorder. Environmental risk factors, on the other hand, were only modestly correlated. The similarity in genetic influences on neuroticism and generalized anxiety disorder raises the possibility that people with high levels of neuroticism could be a useful starting point in the hunt for genes for generalized anxiety disorder.