Differences in pure tone thresholds between ears were evaluated at two different patient care facilities to determine this measure's value as a screen for acoustic neuroma. We evaluated the audiograms of tumor and nontumor groups to estimate the true positive rates and false positive rates for several decision rules. Threshold differences were found to be a more effective diagnostic tool for females than for males. However, even for the most effective rules, the efficiency of this test alone is mediocre, which indicates that hearing threshold differences between ears must be combined with other criteria for a cost-effective approach to acoustic neuroma identification. Furthermore, tumor size was not predicted by the amount of threshold asymmetry between ears, which suggests that some large, potentially life-threatening tumors may be missed if pure tone threshold differences are the sole criterion for referral for additional tests.