We conducted a phase-I study to test the practicability and usefulness of a short (15-30 min) clinical interview for the assessment of cancer patients' spiritual needs and preferences. Physicians assessed the spirituality of their patients using the semi-structured interview SPIR. The interview focuses on the meaning and effect of spirituality in the patient's life and coping system. Visual Analogue Scales (VAS) and Questionnaires were completed following the interview for rating whether SPIR had been helpful or distressing, and to what extent spirituality seemed important in the patient's life and in coping with cancer disease. Thirty oncological outpatients who all agreed to participate were included. The majority wanted their doctor to be interested in their spiritual orientation. Patients and interviewing physicians evaluated the SPIR interview as helpful (patients mean 6.76 +/- 2.5, physicians 7.31 +/- 1.9, scale from 0 to 10) and non-distressing (patients 1.29 +/- 2.5, physicians 1.15 +/- 1.3, scale from 0 to 10). Following the interview, doctors were able to correctly gauge the importance of spirituality for their patients. Patients who considered the interview as very helpful (VAS > 7) were more often female (P = 0.002). There were no differences between patients who evaluated the SPIR as very helpful and those who did not, as far as diagnosis, educational level or belonging to a religious community were concerned. The present study shows that a short clinical assessment of cancer patients' spirituality is well received by both patients and physicians. The SPIR interview may be a helpful tool for addressing the spiritual domain, planning referrals and ultimately strengthening the patient-physician relationship.