In this study, 294 patients with acute proximal DVT (deep venous thrombosis) were randomly assigned to receive intravenous standard heparin in the hospital (98 patients) or low-molecular-weight heparin (LMWH) (nadroparin 0.1 mL [equivalent to 100 AXa IU] per kg of body weight subcutaneously twice daily) administered primarily at home (outpatients) or alternatively in hospital (97 patients) or subcutaneous calcium heparin (SCHep) (99 patients, 0.5 mL bid) administered directly at home. The study design allowed outpatients taking LMWH heparin to go home immediately and hospitalized patients taking LMWH to be discharged early. Patients treated with standard heparin or LMWH received the oral anticoagulant starting on the second day, and heparin was discontinued when the therapeutic range (INR 2-3) had been reached. Anticoagulant treatment was maintained for 3 months. Patients treated with SCHep were injected twice daily for 3 months without oral anticoagulants. Patients were evaluated for inclusion and follow-up with color duplex scanning. Venography was not used. In case of suspected pulmonary embolism (PE) a ventilatory-perfusional lung scan was performed. Endpoints of the study were recurrent or extension of DVT, bleeding, the number of days spent in hospital, and costs of treatments. Of the 325 patients included, 294 completed the study. Dropouts totaled 31 (10.5%); six of the 325 included patients (1.8%) died from the related, neoplastic illness. Recurrence or extension of DVT was observed in 6.1% of patients in the LMWH group, in 6.2% in the standard heparin group, and in 7.1% in the SCHep group. Most recurrences (11/17) were in the first month in all groups. Bleedings were all minor, mostly during hospital stay. Hospital stay in patients treated with LMWH was 1.2+/-1.4 days in comparison with 5.4+/-1.2 in those treated with standard heparin. There was no hospital stay in the SCHep group. Average treatment costs in 3 months in the standard heparin group (US $2,760) were considered to be 100%; in comparison costs in the LMWH group was 28% of the standard heparin and 8% in the SCHep group. This study indicated that LMWH and SCHep can be used safely and effectively to treat patients with proximal DVT at home at a lower cost.