Nonorganic chronic headache is a common, challenging presentation in clinical practice. The aim of this study was to investigate the frequency of associated psychiatric psychopathology, personality disorders, or traits. In addition, the study attempted to investigate possible relationships of nonorganic chronic headache with alexithymia, locus of control, and pain perception. Psychiatric pathology, personality traits, and pain profiles were examined in 100 randomized patients with chronic headache lacking an obvious organic basis, and they were compared with 100 subjects, 50 with headache of a known organic cause and 50 seemingly healthy persons, by using structured clinical interviews. Somatoform pain disorder was diagnosed in 43% of the nonorganic and 20% of the organic headache group. Nine percent of the former group had major depression, 16% had dysthymia, and 8% had both. In the organic group, 56% had no psychiatric disorder and 20% had somatoform pain disorder. Seventy-seven percent of the patients in the nonorganic pain group had personality disorders, mostly of the mixed and multiple types, compared with 24% of the organic headache patients. The study sample was more alexithymic than the other groups (in 65% of subjects) and had a culturally influenced locus of control and a pain profile characterized by dramatization, vagueness, lower pain threshold, and lower pain tolerance. The nonorganic chronic headache patients showed a high prevalence of somatoform, depressive, and other forms of psychiatric disorders. The high frequency of personality disorders, mostly the mixed and multiple types, the high alexithymic pattern, and low pain threshold and tolerance in the study group should be taken into consideration in the evaluation and management of nonorganic headache patients.