The lumbar intervertebral foramens of 20 isolated cadaveric spines were investigated by the use of a molding technique to assess their dimensions accurately and how intervertebral disc pathology altered their configuration. Oval foramens predominated over auricularly shaped foramens when the disc was normal, but when the disc was abnormal, the converse was true. Foraminal size varied from 40 to 160 mm2 but showed great variation even at individual levels; these were not accurately reflected by simple radiologic measurements.