Anxiety comprises many clinical descriptions and phenotypes. A genetic predisposition to anxiety is undoubted; however, the nature and extent of that contribution is still unclear. Methods for the genetic analysis of such complex disorders is briefly reviewed, followed by a discussion of the comorbidity of anxiety with other psychiatric disorders and their possible common genetic etiology. Extensive genetic studies of the serotonin (5-hydroxytryptamine, 5-HT) transporter (5-HTT) gene have revealed how variation in gene expression can be correlated with anxiety phenotypes. Complete genome-wide linkage scans for panic disorder (PD) susceptibility genes have suggested a locus on chromosome arm 7p, and association studies have highlighted many candidate genes. A highly significant association between phobias, panic disorder, and a duplication at chromosomal region 15q24-26 is one of the most exciting findings to date. Emerging molecular genetic technologies and the use of increasingly sophisticated animal models of anxiety provide great promise for the future of the field.