This study is a retrospective single case series. Two hundred and thirty-seven patients were treated with jackyakamcho-tang (JKT) for relief of muscle spasm and pain; 81 of them were included in analysis. (The others were excluded because of insufficient medical records to confirm the diagnosis or assess the response.) There were 29 patients with nocturnal leg cramps, 28 with cervical spondylosis, 13 with thalamic pain and 11 with carpal tunnel syndrome, for which the effectiveness was assessed as 86.2%, 60.7%, 45.5% and 72.8%, respectively. Adverse effects (indigestion, diarrhea or edema) were seen in 11.1% of the total patients, but severe cases were only 3.7%. Taking the effectiveness and the safety into consideration, the usefulness was assessed as 86.2%, 57.1%, 53.9% and 72.8% for treating nocturnal leg cramps, cervical spondylosis, thalamic pain and carpal tunnel syndrome, respectively. In conclusion, we suggest that JKT is a useful herbal medicine with analgesic and anti-spasmodic effects.