A measurement experiment regarding willingness to pay for antihypertensive therapy is reported. A new type of binary willingness to pay question is used, that allows for different degrees of certainty with respect to the responses. Mean willingness to pay is derived from a simple expected utility model and estimated using maximum likelihood methods. The estimated parameters are highly significant, with predicted signs, and imply a mean willingness to pay of about SEK 800 ($130) per month. The explanatory power of the equation that only includes 'certain' yes/no responses is, as expected, much higher than that of the equation where only 'uncertain' responses are included.