We undertook a literature synthesis of CT, MR, and myelographic studies to evaluate what is known about the diagnostic accuracy of these imaging tests for the diagnosis of lumbar spinal stenosis in adults without prior surgery. From 116 possibly relevant studies, we reviewed 14 articles that included cases of spinal stenosis with a reference standard other than the imaging tests of interest. Of the studies we reviewed, two involved only MR, nine only CT, and three used both; six studies included myelography. Rating categories of A, B, C, or D were assigned for the quality of research methods used to estimate diagnostic accuracy. All studies received either a C or D rating. Common methodologic problems were failure to assemble a representative cohort for study, small sample size, and failure to maintain independence between image readings and reference standards. Sensitivity ranged from 0.81 to 0.97 for MR, from 0.70 to 1.0 for CT, and from 0.67 to 0.78 myelography. Studies varied greatly in case selection, definition of test and disease categories, and geographic locale, so no pooled estimates could be derived. In asymptomatic patients, abnormal findings appeared on CT or MR in 4-28% of cases and were more common in the elderly. Published studies of the value of CT and MR for the diagnosis of lumbar stenosis lack methodologic rigor and do not permit strong conclusions about the relative diagnostic accuracies of these procedures. For the present, the choice between MR or CT depends on issues such as costs, reimbursements, access to equipment, skill of radiologists, and patient safety. Better studies will be needed to document claims for improvements in imaging accuracy as MR technologies evolve. These studies should emphasize larger sample sizes, more attention to research designs that avoid methodologic biases, and the contribution of imaging diagnoses to ultimate clinical outcome.