The authors undertook a prospective double-blind, controlled trial to investigate the effect of prophylactic low-dose heparin/dihydroergotamine, low-molecular heparin/dihydroergotamine and a placebo on the blood pressure and postural hypotension on postoperative mobilization. A material of 120 patients admitted for hip surgery was subdivided at random into three groups. Examination for postural hypotension was undertaken on the fifth postoperative day. No significant differences were present between the three groups as regards age distribution, systolic and diastolic blood pressures and pulse rates. This investigation did not reveal any significant effect of the antithrombotic combined treatment with heparin/dihydroergotamine on the blood pressure or postural hypotension on postoperative mobilization following elective hip surgery. No cases of ischaemic side effects were observed. However, this investigation cannot disprove a slight hypotensive effect and, for this reason, this treatment should be contraindicated in patients with circulatory disturbances.