Deep venous thrombosis (DVT) is common after lower limb injury, but the effect of prophylactic treatment has not been documented in large randomised trials or meta-analyses. As a result, evidence-based recommendations have not been established. The purpose of this study was to evaluate the incidence of venous thromboembolism in patients with Achilles tendon rupture. A total of 100 consecutive patients with an acute Achilles tendon rupture were included in a prospective study and randomised to either surgical or non-surgical treatment. At 8 weeks after the initiation of treatment, 95/100 patients were screened for DVT using colour duplex sonography (CDS) with blinded interpretation by two experienced examiners and adjudication in cases of disagreement by a third person. A total of 95 patients (79 male and 16 female) with a median (range) age of 41 (24-63) years were screened for CDS at 8 weeks. Of the 95 patients, 32 had a CDS-verified thrombosis, 5 proximal and 27 distal, whereas 3 had non-fatal pulmonary embolism. Surgical treatment was performed in 49 patients, non-surgical in 46. There were no significant differences in DVT frequency between the two treatment groups. The incidence of asymptomatic and symptomatic deep venous thrombosis is high after Achilles tendon rupture and there is a need to define the possible benefit of thromboprophylaxis.