A modified method is given for the precolumn derivatization and subsequent high-pressure liquid chromatographic seperation of 3-methylhistidine from urine. The elution contained isocratic solution with acetonirile and 10 M sodium phosphate(pH 7.5) requires less than 7 min. The recoveries of 3-methylhlstidine from urine control were 95% to 106%. 3-Methylhistidine determinations were performed on urine samples from volunteers who were both male trained and non-trained physical undergraduates. As the result, urinary .3-methylhistidine content of volunteers increased significantly after weight training.