Aims and background. To assess the safety and feasibility of neutron brachytherapy (NBT) combined with external beam radiation (EBRT) in the treatment of patients with inoperable gastroesophageal junction adenocarcinoma (GEJAC). Methods and study design. From January 2001 until November 2011, 67 patients with inoperable GEJAC received EBRT combined with NBT. Radiotherapy consisted of EBRT up to a total dose of 40 to 54 Gy in 20 to 27 fractions and NBT up to 12 to 25 Gy in 3 to 5 fractions. The patients were divided into 2 total-dose groups: a low-dose group (28 patients, 52 to 57 Gy) and a high-dose group (39 patients, 58 to 69 Gy). Results. The duration of follow-up ranged from 16 to 106 months. The median survival time for the 67 patients was 15.7 months, and the 1-, 2-, 3- and 5-year rates for overall survival (OS) were 56.7%, 37.2%, 30.8% and 12.7%, respectively. The corresponding local-regional control (LRC) rates were 72.4%, 59.1%, 51.2% and 42.0%, respectively. In univariate analysis, the 5-year OS rates were 7.1% and 16.5% for patients of the low-dose and high-dose groups, respectively (P = 0.024). The incidence of acute esophagitis (grade >= 2) was significantly higher in the high-dose group (56.4%) than the low-dose group (32.1%) (P = 0.049). No fistulas or massive bleeding were observed during treatment. Six of the 67 patients (9.0%) experienced late toxicity: fistulas developed in 3 patients and massive bleeding occurred in 3 patients. Of these 6 patients, 4 had persistent or locally recurrent tumors, and 2 displayed no evidence of tumors. Three patients each were in the low-dose and high-dose groups. Conclusions. The combination of EBRT and NBT was safe and effective in patients with GEJAC. The high-dose group achieved better LRC and OS but had a higher rate of acute esophagitis.