This paper reports on the initial efforts to validate a brief self-report inventory, the Systems of Belief Inventory(SBI-15R), for use in quality of life (QOL) and psychosocial research studying adjustment to illness. The SBI-15R was designed to measure religious and spiritual beliefs and practices, and the social support derived from a community sharing those beliefs. The authors proposed this scale to address the need for greater exploration of spiritual and religious beliefs in QOL, stress and coping research. Phase I: Item generation. The research team identified four domains comprised of 35 items that make up spiritual and religious beliefs and practices. The instrument was piloted in a structured interview format on 12 hospitalized patients with varying sites of cancer. Phase II: Formation of SBI-54. After these initial efforts, the research team increased the number of items to 54 and adopted a self-report format. To assess patients reactions to the questionnaire, the new version was piloted on 50 outpatients with malignant melanoma. Phase III: Initial validation. To begin establishing validation, 301 healthy individuals with no history of cancer or serious illness in the prior year were asked to complete the SBI-54 and several other instruments. A principal components analysis with varimax rotation of the SBI-54 identified two factors, in contrast to the four which were hypothesized, one measuring spiritual beliefs and practices, the other measuring social support related to the respondent's religious community. Phase IV: Item reduction of the SBI-54. A shortened version of the SBI-54 with 15 items, five from the items identifying factor I and ten from those identifying factor II, was developed to lessen patient burden. The new SBI-15 correlated highly with the SBI-54, and demonstrated convergent, divergent, and discriminant validity. Revision of SBI-15. The investigators rephrased one statement in order to broaden the applicability of the SBI-15 to patients other than those with a diagnosis of cancer, and to healthy individuals. DISCUSSION. The SBI-15R met tests of internal consistency, test-retest reliability, and convergent, divergent, and discriminant validity in both physically healthy and physically ill individuals. The SBI-15R may have value in measuring religious and spiritual beliefs as a potentially mediating variable in coping with life-threatening illness, and in the measurement of QOL.