PURPOSE: To determine the diagnostic value of CT-guided biopsy or aspiration of the spine and paraspinal soft tissue in infectious spondylitis. MATERIALS AND METHODS: Between January 2000 and June 2002, 58 patients underwent 67 biopsies and/or aspirations under CT guidance to identify the organism causing infectious spondylitis, and were included in this study. Nine underwent rebiopsy. In all patients, MR images were available before biopsy and/or aspiration. In 63 of 67 procedures, the specimens or aspirates obtained were prepared for culture and smear, and for histological examination, four procedures involved aspiration only. In ten patients with suspected tuberculosis, a polymerase chain reaction test was performed. For all procedures, the transpedicular, transcostovertebral or paravertebral route was involved, according to the level and shape of the lesions, and 14-, 16-, or 18-gauge core biopsy needles and/or 20-gauge aspiration needles were employed. Lesions invloved a paravertebral (n=17), psoas (n=8) or epidural (n=1) abscess; an intervertebral disc (n=20); or a vertebral body (n=21). The levels at the mid-thoracic spine were T4-T10 (n=11); at the thoracolumbar junction, T11-L1 (n=14); at the lumbar spine, L1-L4 (n=25); and at the lumbo-sacral junction, L5-S1 (n=17). In nine of 58 patients, rebiopsy was performed. RESULTS: Diagnosis was confirmed in 22 of 58 patients (38%), and was as follows: tuberculous spondylitis (n=17), pyogenic spondylitis (n=4), and fungal spondylitis (n=1). Thirty-six unconfirmed cases were diagnosed as nonspecific inflammation (n=21), fibrosis involving cortical bone (n=1), necrotic material (n=5) and inadequate specimen without evidence of malignancy (n=9). Only one of the nine cases in which biopsy was repeated was confirmed as tuberculous spondylitis. Diagnosis was confirmed in 7 of 17 paravertebral abscesses (41%), 8 of 21 vertebral bodies (38%), 6 of 20 intervertebral discs (30%) and 1 of 8 psoas abscesses (13%). CONCLUSION: In infectious spondylitis, the overall diagnostic yield of CT-guided needle biopsy and/or aspiration is relatively low, but the procedure seems to be effective for excluding malignancy. In identifying the organisms involved in infectious spondylitis, a paravertebral lesion is in a more favoured location than a psoas lesion.