Age effects on the ability to ignore irrelevant auditory information were studied using frequency discrimination threshold (FDT) tasks. FDTs were determined in an unmasked condition with target tones in isolation, and in two backward-masked conditions with a nontarget masking tone presented 20 to 240 ms after the target. One masked condition included irrelevant variability in the masker frequency, but the other did not. The no-variability condition yielded more masking in older than in young adults. Masker variability induced large FDT elevations in both groups; however, the improvement in FDTs with training was large in young but only minimal in older adults.