The Patient Needs Assessment Tool (PNAT) is an interviewer-rated scale that may be completed through a simple structured interview and screens cancer patients for potential problems in physical and psychosocial functioning. The instrument provides separate scores for physical, psychological, and social status, and can potentially clarify the types of interventions needed to address specific areas of dysfunction. Reliability and validity was tested in two studies that used prescreened patient videotapes and other materials to assess the performance of the PNAT in groups of oncology nurses, physicians, and social workers. The data demonstrate that subscale scores for the physical, psychological, and social dimensions have good inter-rater reliability and internal consistency (intraclass correlation coefficients of 0.71-0.97). Criterion and construct validity was suggested through high correlations of each subscale with the evaluation of expert raters (correlation coefficients of 0.85-0.95) and with scores on validated patient-rated instruments appropriate to the functional area. These analyses suggest that the PNAT is a valid scale for the assessment of a range of functional disturbances in the cancer population.