197 spine CTs were performed from 29th, March 1982 to 7th March, 1984. Among them, 39 patients preoperativelydiagnosed as herniated nucleus pulposus ar bulging disc with CT and myelography were operated. 43 disc spaces ofdisc disease were analysed in true positive and false negative cases. Finally the accuracy, sensitivity andspecifictiy of spine CT and myelography ar calculated. The resuslts are as follows; 1. The CT findings of discdiseases are in order of frequency, asymmetrical obliteration of epidural fat (82%), ventral indentation orcompression on dural sac(72%), focal protrusion of disc(64%), root changs - obliteration, displacement,compression, non-filling of meterizamide - (54%), diffuse disc bulging (36%), disc at body level(31%), disccalcifications (26%), disc vacuum (10%) and other associated findings -spinal stenosis, foraminal stenosis,legament flavum thickening, facet joint hypertrophy -(26%). 2. Sensitivites of spine CT and myelography are 95%and 94%, specificities are 67%, 50% and overall accuracies 93%, 87%, respectively. 3. Therefore, it is recommendedthat the spine CT be used as primary diagnostic method and the myelography as a secondary complementary study whenthe CT gives no conclusive findings.