OBJECTIVE To assess the efficacy, toxicity, and the optimum dose of high-dose-rate brachytherapy following chemoradiotherapy (CRT) compared with a historical group of patients treated with a combination of external beam and brachytherapy (RT alone). METHODS Fifty-three patients with localized esophageal cancer received concurrent chemoradiotherapy followed by brachytherapy. The chemotherapy regimen was a combination of cisplatin 60 mg/m2 on day 1 and fluorouracil 600 mg/m2 continuous infusion from days 1-4 during the first and last week of external irradiation. Radiotherapy consisted of external irradiation to a total dose of 40-61 Gy (median 50 Gy) and brachytherapy to 8-24 Gy (median 16 Gy) in 2-4 fractions. RESULTS Acute toxicity was well tolerated. A fistula occurred in one patient 1 week after completion of external irradiation. Local control was achieved in 32/53 (60%) compared with 42% of the RT group (p = 0.029). Local control rates of the CRT group were significantly better than those of the RT group in Stages II and III. Late toxicity (esophageal ulceration and strictures) occurred in 18 (34%) of the CRT group compared with 12% in the RT group (p = 0.013). Severe late toxicity (RTOG/EORTC criteria Grade 3-4) occurred in six patients (15%) whose chemotherapy was followed by 16-24 Gy via brachytherapy compared with 2.5% in the RT group (p = 0.010). CONCLUSIONS Combined chemoradiotherapy and brachytherapy boost achieved better local control than radiotherapy alone. However, a high level of severe late toxicity was observed especially with 16-24 Gy via brachytherapy.