Data from humans and animal models provide evidence for an age-dependent impairment in the ability to localize sound. The lateral superior olive (LSO) in the ascending auditory pathway is one important center involved in processing of binaural auditory stimuli. To identify potential age-dependent changes we characterized the LSO in young (< 15 months) and old (> or =3 years) gerbils with a special emphasis on the expression of GABA- and glycine-like immuno-reactivity. The dimensions of the LSO, as well as the number and density of glycine- and GABA-immuno-reactive neurons, were not significantly different between young and old gerbils. The size of glycine- and GABA-immuno-reactive neurons was significantly reduced in the high-frequency (medial) limb of the LSO. Over all, age-dependent changes in the LSO of the gerbil were small.