By using 24 hour urinary creatinine levels, skeletal muscle mass (kg), its rate (%) of body weight and creatinine height index (%) were determined in old Japanese women suffering from walking difficulty in nursing home and compare with those of young university students. Those of old subjects showed approximately 30-50%, 36-44% and 44-46% of young subjects, respectively. It is suggested that these values are important and useful biomarkers for the planning and the achievement of rehabilitation program for the maintaining and restoring skeletal muscle mass and for the careful support by registered care workers to aged persons.