Myalgia/arthralgia is a crucial side effect of paclitaxel, and may become the major dose-limiting side effect. However, this is a situation where there is little effective preventive treatment. L-Glutamine was reported as a neuroprotective agent for vincristine-induced neurotoxicity. In Japan, there have been reports on steroid and Shakuyaku-Kanzou-to (a herbal medicine) for paclitaxel-induced myalgia/arthralgia. This study aimed to compare the effect of L-Glutamine and Shakuyaku-Kanzou-to, and to discuss the validity of these agents for the paclitaxel-induced myalgia/arthralgia. Our results suggested that Shakuyaku-Kanzou-to showed no remarkable effects against paclitaxel-induced myalgia/arthralgia as had been reported before; however, both L-Glutamine and Shakuyaku-Kanzou-to decreased the duration of grade 2 toxicity (CALGB Expanded Common Toxicity Criteria) in comparison with those who were not treated. L-Glutamine and Shakuyaku-Kanzou-to might therefore a preventive effect against moderate or severer myalgia/arthralgia during paclitaxel-treated chemotherapy. Further trials are needed to confirm the value of these drugs.