The efficacy and tolerability of O-(β-hydroxyethyl)-rutosides (HR) in elderly patients (aged over 65 years) with chronic venous insufficiency or varicose veins was studied in a multi-centre, double-blind, randomised, placebo-controlled trial. Of the 104 patients entered into the trial, data from 102 were available for analysis of tolerability and from 86 for efficacy. Treatment was for 6 months, with monthly examinations. Three different dosages were used due to slight differences in the registered dosage in various countries: (1) 250 mg 4 times daily (1 g/ day), UK, n = 19 patients; (2) 300 mg 3 times daily (900 mg/ day), FRG and Belgium, n = 55, and (3) 300 mg 4 times daily (1,200 mg/day), The Netherlands, n = 30. Each centre had its own placebo control group. The HR-treated group (n = 41) showed a significantly greater reduction in the total symptom score, 5.7 ± 2.4 to 2.3 ± 1.8, than in the placebo group, 4.4 ± 3.0 to 3.0 ± 2.4 (p < 0.01). Of the 5 studied symptoms there was also a significant (p < 0.05) improvement in leg cramps, heavy legs and restless legs. No significant differences between the two groups were seen for aching pains and paraesthesia. A small reduction was also seen in ankle and calf circumferences, which became significant at the end of the trial (p < 0.05). Pitting oedema of the leg (p < 0.01) and eczema of the leg (p < 0.05) also improved significantly greater than in the control group. Tolerability, as reflected in adverse events and monitoring of a range of 31 laboratory tests, was comparable in the HR group to that of the placebo group. HR appears to be an effective and well-tolerated treatment for symptoms related to chronic venous insufficiency or varicose veins in elderly patients.