The accuracy of computerized tomography (CT) in diagnosing herniated discs has been well established. Huge herniated discs, which paradoxically may be very subtle, have been mentioned but not stressed as potential causes of false-negative diagnosis. Five cases during a 5-year period encompassing approximately 2500 examinations have been encountered by the authors. In this experience, the most consistent finding is the subtle increased density of the disc compared with the dural sac. The diagnosis is aided by awareness that huge discs severely compressing the dural sac may be very subtle; the use of narrower windows for CT scanning, sagittal re-formation, and occasionally the use of myelography with or without repeat CT scanning may also assist.