A questionnaire was sent to 1000 patients with Raynaud's phenomenon (RP) and an equal number of controls in order to accumulate one of the largest patient data banks currently available. Five-hundred and seventy-one correctly completed paired returns were processed so as to investigate the association between Raynaud's phenomenon and other factors suspected of influencing the condition. The involvement of female sex hormones in RP was indicated by the predominance of women (93%), a 6% (P less than 0.02) higher incidence of infertility and the influence of menstruation (15%), the menopause (73%) and pregnancy (53%) on symptoms. Patients with scleroderma had a 5% higher incidence of stillbirths. A familial predisposition for RP was noted dependent on age at onset of symptoms (age less than 30, 14% greater than 30, 4.9%). The Raynaud's group overall had a significantly higher percentage who had been treated for migraine (7% higher P less than 0.01), angina (3% higher P less than 0.05) and duodenal ulcer (3% higher P less than 0.001). Of the respondents who had undergone sympathectomy (n = 140, 24.5% of the total), 18.6% claimed lasting benefit and 66.4% claimed no benefit after one year. The mean age at sympathectomy was 38.6 years (S.D. +/- 13 range 14-78) with a mean age of start of symptoms of 29.2 years (S.D. +/- 14.7, range 0-70). There was no significant difference between the effects of sympathectomy on those patients with and those without associated conditions.