In this preliminary study we examined the enhancing effect of D-phenylalanine on acupuncture anesthesia. We made 4 different kinds of experiments with 3 volunteers. The results show that D-phenylalanine extends the analgesic effect of acupuncture analgesia remarkably, with no exception in 3 cases. According to these facts, we believe that these findings have an important meaning for those who are engaged in acupuncture treatment or research.