One hundred and fifty-four patients, who had been subjected to phlebography 5-8 years previously because of clinical suspicion of deep venous thrombosis (DVT), were investigated to evaluate the frequency of deep venous insufficiency (DVI). The evaluation included clinical examination, registration of subjective complaints and objective measurements with plethysmography, venous pressure and Doppler ultrasound. DVT had been present in 75 legs. There were no statistically significant differences between legs with and without earlier DVT apart from more venous outflow obstruction in the former. DVI was as common after calf vein thrombosis as after more proximal DVT. DVI was more frequent in elderly patients and in patients with a history of previous DVI or DVT. The sufficiency of the popliteal vein seemed to be of great importance in the development of DVI. More than one third of legs without DVT had developed DVI at follow-up.