Background. Spiritual beliefs are rarely considered in psychological or medical publications. We recently published the psychometric properties of an interview designed to measure religious and spiritual belief. In this study, we aimed to develop this instrument further as a self-report questionnaire and to make it more comprehensive by including measurement of spiritual experiences in addition to faith or intellectual assent.

Methods. Based on extensive discussion with colleagues, advice from users of the interview and comments from respondents, a self-report format was designed. We then evaluated the final format of the questionnaire in terms of (1) patterns of response and demographic predictors of beliefs; (2) test–retest reliability and internal consistency; (3) criterion and internal validity; and (4) the nature of spiritual experiences and their relationship to beliefs and strength of beliefs.

Results. Two hundred and ninety-seven people took part in the validity and reliability tests of the questionnaire. Criterion validity, predictive validity, internal consistency and test–retest reliability were acceptably high. The instrument consistently differentiated between people with high and low spiritual beliefs.

Conclusions. This instrument is brief and simple to complete. We would recommend that measures of religious and/or spiritual belief like this be more widely applied in health services research as they evaluate aspects of people's lives that go somewhat further than health status or quality of life.