This paper critically reviews the methodology used in clinical trials in chronic occlusive arterial disease (COAD) stage II (intermittent claudication) patients. The reasons for choosing internationally accepted standard treadmill settings as well as its limitations are discussed. Emphasis is put on the discussion of valid trial endpoints such as hemodynamic surrogates and clinically oriented parameters. Reasons for a spontaneous and treatment-unrelated improvement in claudication distance are elucidated, and variables which may be used for the definition of patient subsamples showing a high frequency of a pronounced treatment response (treatment responder populations) are presented. The magnitude of claudication distance improvement that might be considered clinically relevant is discussed in the light of the European Union guidelines for clinical trials in COAD patients. Results achieved with pentoxifylline are presented in context with all variables mentioned above.