BACKGROUND: Techniques for identification of the epidural space have advantages and disadvantages. We made an electronic apparatus to ensure an epidural space by detecting the reduction of pressure. We investgated the instrument to see if this could be adequately used for identification of the epidural space. METHODS: Thirty adult patients scheduled to receive an epidural injection for surgery were selected for the investigation. We connected the apparatus with an epidural Tuohy needle of which the tip was in the ligamentum flavum. We injected air to increase the pressure inside the epidural needle to 50 mmHg or 100 mmHg, and then the epidural needle was advanced slowly until we heard the alarm from the epidural detector when pressure inside the epidural needle suddenly decreased under the set point, suggesting the epidural needle reached the epidural space. After ensuring the epidural space we injected the anesthetics to induce epidural anesthesia. RESULTS: In both groups, we obtained successful anesthesia results and there were no complications. The volume of air injected into the epidural space was 0.64 +/- 0.1 in 50 mmHg group and 0.95 +/- 0.2 in 100 mmHg group. CONCLUSIONS: The use of the epidural detector in 30 patients demonstrated that this instrument could be a safe and effective means of identifying the epidural space. It allows the reduction of air injected into the epidural space, reducing the chance of complications due to an overinjection of air.