Prolonging thromboprophylaxis after hospital discharge following surgery reduces the incidence of venographic and symptomatic venous thromboembolism (VTE), although the effects on post-thrombotic syndrome are not yet clear. Oral anticoagulants and low-molecular-weight heparins (LMWHs) may be used for extended outpatient therapy, but oral anticoagulants require frequent laboratory monitoring and may cause major gastrointestinal bleeding. Conversely, LMWHs are effective and safe at a fixed, once-daily dosage without monitoring. Four studies have shown that extended prophylaxis with LMWHs significantly reduces the incidence of post-discharge VTE following total hip replacement. However, the need for subcutaneous injection potentially limits home use of LMWHs outside clinical trials because the amount of drug administered may vary between injections if patients self-inject, while administration by nurses would be too costly. An auto-injection device is now available for administering the LMWH enoxaparin. The device is simple to use and delivers a precise pre-determined dose. During studies with such devices, volunteers successfully performed mock injections and patients with indications for thromboprophylaxis showed high levels of acceptance with administration for up to 3 weeks. Ongoing studies are assessing longer periods of self-administration.