Study objectives: We determine the accuracy of noncontrast helical computed tomography (NHCT) compared with that of intravenous pyelography (IVP) in diagnosing acute urolithiasis. Methods: Computerized searches of MEDLINE and EMBASE were combined with hand reviews of major journals and of articles from reference lists. Articles were assessed according to a priori criteria for inclusion. Study eligibility was independently assessed by 2 reviewers in a blinded fashion. Test results were combined and analysis of log-transformed data was conducted by using general linear models. Results: No disagreement was found between the 2 investigators in terms of articles that met the inclusion criteria or between the results of the studies. Four studies involving a total of 296 patients met all of the a priori criteria. The pooled positive likelihood ratios (LR+) for NHCT and IVP are 23.15 (95% confidence interval [CI] 11.53 to 47.23) and 9.32 (95% CI 5.23 to 16.61), respectively. The pooled negative likelihood ratios (LR−) for NHCT and IVP are 0.05 (95% CI 0.02 to 0.15) and 0.33 (95% CI 0.23 to 0.48), respectively. The differences between NHCT and IVP were statistically significant for both LR+ (P=.046) and LR− (P=.013). Differences among trials were not statistically significant in either analysis (P=.125 for LR+; P=.114 for LR−). Conclusion: The studies analyzed consistently demonstrated NHCT to be superior to IVP in accurately diagnosing acute urolithiasis, and differences between the 2 tests for both LR+ and LR− were statistically significant. [Ann Emerg Med. 2002;40:280-286.]