We evaluated the incidence of postoperative extradural hematomas by means of magnetic resonance imaging (MRI) technique in 44 patients who underwent successful surgery for a virgin lumbar disc herniation. Of these patients, 28 were treated with microdiscectomy and 16 with percutaneous nucleotomy. Postoperative hematoma proved to be a universal MRI finding in the microsurgically treated patients: hematomas were found in all patients in the microdiscectomy group. In 12 (43%) patients the hematoma extended into the dural sack. The incidence of hematomas was significantly (p = 0.001) lower in the patients treated with percutaneous nucleotomy: hematomas were detected in only 10 (63%) of the 16 patients in the nucleotomy group. The hematomas in these patients were also smaller in size and none of them connected with the dural sac. Correlation between the hematomas and clinical findings showed that the presence of a hematoma had no obvious effect on the immediate postoperative recovery of a patient.