Background: Post-dural puncture headache (PDPH) is one of the well-known complication of spinal anesthesia. Epidural blood patch is the treatment of choice for PDPH but is rarely used for the prevention of PDPH after spinal anesthesia. The purpose of this study is to observe the effectiveness of epidural blood patch for prevention of PDPH and to evaluate the complications after epidural blood injection. Methods: Three hundred patients (ASA I or II) receiving spinal anesthesia were studied. They were randomly devided into two groups. Patients in Group I, the control group, were maintained in a supine position for 24 hour after spinal anesthesia. Patients in Group II, the study group, received 3 ml of autologous blood in the epidural space after spinal anesthesia. PDPH was evaluated for 5 days. The incidence, location, onset, and duration of headache in the patients presenting with PDPH were measured for 5 days, and the complications following epidural blood patch in Group II were observed for 2 weeks. Results: The incidence of PDPH in group I was 11%, but 0% in group II. There were no specific complications following epidural blood patch in Group II. Conclusions: This study suggest that the 3 ml epidural autologous blood patch is an useful method for the prevention of PDPH in patients with spinal anesthesia.