Objective To evaluate the incidence of complications of intrathecal baclofen (ITB) therapy for spasticity in Japan, where a unique training course and nationwide registration are required. Materials and Methods An analysis of complications was performed in all patients who underwent ITB in Japan from 2005 to 2011. Prior to surgery, all the doctors involved took a one-day training course, which included hands-on training. Surgical techniques that avoided complications were emphasized. Results A total of 406 pumps were implanted in 400 patients (277 men, 123 women) having severe spasticity. Because this study is currently in progress, among the 400 patients, 78.3% (313/400) had finished a one-year observation follow-up. There were 369 adult and 31 juvenile (under 17 years old) patients, including 12 patients under nine years old. All-cause adverse events were seen in 148 patients (37%), and 93 (23.3%) of these were regarded as severe. Catheter problems were observed in 34 (8.5%) patients: catheter migration in 25 (6.3%), breakage in 6 (1.5%), obstruction in 2 (0.5%), kinking in 1 (0.3%), and dislodgement in 1 (0.3%). Pump trouble was observed in seven (1.8%) patients: alarm abnormality in one (0.3%), memory error in one (0.3%), delayed recovery in one (0.3%), rotation in one (0.3%), malfunction in one (0.3%), and abnormal infusion rate in two (0.6%). Device-related and surgical wound infection occurred in 12 patients (3%), and nine were regarded as severe. Leakage or subcutaneous accumulation of the cerebrospinal fluid was seen in 13 patients (3.3%). Conclusion The requirement of taking of a training course before starting ITB seemed to reduce complications. Although there were surgery-related complications, the rate of complications in Japan appeared to be lower than those reported in larger series of ITB. However, whether the reported rates can be primarily ascribed to a mandatory training course requires further investigations.