The present study investigates whether physiological activity may play a part in maintaining the amplified perception of bodily processes typical for somatization. Eighty-one persons were classified into three groups by means of a structured clinical interview: 24 patients with somatization syndrome, 34 patients with somatization syndrome and comorbid major depression, and 23 healthy controls. Subjects completed four blocks of an attentional task, each of the blocks separated by resting periods. Physiological patterns demonstrated higher activity during mental tasks than during rest. The heart rate deceleration after changing from mental challenge to rest was less pronounced in the groups of patients with somatization syndrome than in controls. Moreover, patients with somatization syndrome reported feeling more and more tense during the investigation, while controls showed the tendency to habituate. The effects of heart rate and of feelings of tension partly replicated earlier findings, and demonstrated that physiological activity may interact with psychological processes in somatization.