We analysed 13 cases of lumbar disc infection following surgical discectomy. Two groups of patients were identified. The six patients in group A reported that the initial symptoms of discitis had appeared a mean of 15 days after surgery; on average, antibiotic treatment was started 31 days following operation and continued for 62 days, and symptoms regressed after 3.9 months. Four patients showed moderate changes, while two had extensive osteolytic lesions of one or both vertebral bodies adjacent to the involved disc. In the 7 cases in group B, discitis was suspected a mean of 5 days and antibiotics were initiated a mean of 8 days following surgery; on average, symptoms regressed 1.8 months after operation. Only four patients showed vertebral radiographic changes and none had marked destructive lesions. In both groups erythrocyte sedimentation rate exceeded 70 mm/h in cases in which discitis was suspected. Tomograms and magnetic resonance studies were the most diagnostic imaging studies in the initial stages of the disease. All patients obtained satisfactory clinical results at the last follow-up. Careful observation of the early postoperative clinical course usually allows detection of disc space infection. Early and adequately prolonged antibiotic treatment may shorten the course of the disease and avoid extensive osteolytic vertebral lesions.