BACKGROUND: Using a disease specific questionnaire, the CLAU-S, we undertook a double blind, placebo controlled study in patients with intermittent claudication to determine whether the increase in the pain-free walking distance, previously demonstrated with naftidrofuryl, is reflected as an improvement in the patients' quality of life. PATIENTS AND METHODS: 287 patients, with stable intermittent claudication for at least 3 months were entered into the study. Following an initial one month placebo run-in, patients were randomised to either naftidrofuryl, at a dosage of 200 mg three times daily, or matching placebo, for 6 months. All patients completed the self-administered CLAU-S questionnaire which is divided into 6 dimensions, before the start of treatment, at 3 and 6 months. Statistical analysis was undertaken on an intention-to-treat (ITT) basis which included all patients know to have taken at least one dose of the drug and to have provided key data on at least one occasion after baseline. For each of the CLAU-S dimensions the two groups were compared with respect to difference between the initial and final values. RESULTS: 255 patients (133 naftidrofuryl, 122 placebo) were eligible for the ITT analysis. Significant improvements, in favour of the active medication, were seen for the dimensions "daily living", "pain", "disease specific anxiety" and "mood". A multivariate analysis of covariance, which took into account such factors as initial score, age and sex confirmed the global superiority of naftidrofuryl (p = 0.004). CONCLUSIONS: In this placebo controlled study, using a disease specific questionnaire, naftidrofuryl has been shown to significantly improve several aspects of the quality of life of patients with intermittent claudication.