Policy makers and practitioners need to differentiate between patient preferences which are strongly held, and those which are not. This study measured not only women's preferences for medical abortion versus surgical vacuum aspiration, but also the strength of these preferences, using a 'willingness to pay' (WTP) technique. Fifty women were recruited and interviewed prior to and following termination of early pregnancy. Due to the sensitivity of the situation, the WTP approach was administered by interview. Results revealed that 34 (64%) preferred to have the medical method. The amounts offered for each method were similar; however, a minority gave higher values for the medical method, thus for those women their strength of preference for that method was more intense. Validity of the technique was supported by the finding of a positive association with social class and the importance women attached to having choice. It is argued that WTP is an acceptable method for the elicitation of strength of treatment preferences. Its further use by nurses and midwives to assess health care preferences should be explored, particularly when considering aspects of care which are traditionally difficult to identify and measure.