After several years of treatment for type 2 diabetes mellitus, a 69-year-old Japanese man developed an acute painful neuropathy, characterized by bilateral causalgia and dysaesthesia in his cheeks and around his eyes, typically 30 min to 3 h after meals. As his glycaemic control deteriorated, his haemoglobin (Hb) A1c level gradually increased from 7 - 8% to 10.3% and his symptoms became more severe. The pain radiated out along the distribution of the ophthalmic and maxillary divisions of the trigeminal nerve. The patient was treated with insulin therapy and his HbA1c level decreased from 10.3% to 6.8% within 7 months. Five months after initiating insulin therapy, his symptoms showed a dramatic improvement. This was a very unusual case of bilateral acute painful neuropathy that involved the ophthalmic and maxillary divisions of the trigeminal nerve, and in which aggravation of the symptoms clearly related to poor glycaemic control.