This prospective investigation was conducted to evaluate the efficacy of different volumes of epidural blood patch (EBP) for treatment of postdural puncture headache (PDPH) in 81 consecutive patients. In the first part of the investigation (Study part I), 10 ml of blood was injected for EBP in 28 patients. In the second randomized part of the investigation (Study part II), the patients were allocated to receive for EBP either 10 ml (27 patients) or 10-15 ml (26 patients), according to the height of the patient. The procedure was considered initially successful if PDPH disappeared completely during the 2-h recovery room follow-up. To evaluate the long-term success, a questionnaire was mailed to all patients. The EBP performed 3.7 +/- 2.9 days following the dural puncture was initially successful in 88-96% of the patients in the different study groups. In the questionnaire, only 50-68% of the patients reported that PDPH had disappeared immediately without recurrence. In 16-36% of the patients the PDPH returned at lesser intensity and in 14-17% PDPH was reported to have continued, disappearing gradually in all patients. Despite this, 87% of all patients were satisfied with the EBP treatment. There were no statistically significant differences between the groups. The results indicate that a larger, height-adjusted volume of blood for EBP in adults does not produce a better effect on PDPH compared to a standard 10-ml volume. Despite the excellent initial effect (91%) seen in our patients, a permanent effect of the blood patch was only achieved in 61%.