OBJECTIVE: The aim of this project was to develop an appropriate and valid instrument for assessment by medical professionals in Japanese palliative care settings. METHODS: We developed a Japanese version of the Support Team Assessment Schedule (STAS-J), using a back translation method, and tested its reliability and validity. In the reliability study, 16 nurses and a physician who work in a palliative care unit evaluated 10 hypothetical cases twice at 3-month intervals. For the validity study, external researchers interviewed 50 patients with matignancy and their families and compared the results with ratings by the nurses in the palliative care unit. RESULTS: Our results with hypothetical cases were: interrater reliability weighted kappa = 0.53-0.77 and intrarater reliability weighted kappa = 0.64-0.85. In the validity study comparing nurse evaluations and the results of interviews with patients and families, complete agreement was 36-70%, and close agreement (+/-1) was 74-100%. As a whole, weighted kappa were low: between -0.07 and 0.51. Our results were similar to those in the United Kingdom and Canada. SIGNIFICANCE OF RESULTS: Although this research was conducted under methodologically limited conditions, we concluded that the STAS-J is a reliable tool and its validity is acceptable. The STAS-J should become a valuable tool, not only for daily clinical use, but also for research.