We explored the ability to discriminate between echolocation calls of 20 adult and 20 juvenile big brown bats (Eptesicus fuscus). Variables describing each call were entered into discriminant function analyses (DFAs) to assess the success of call separation by age, sex, and individual. In agreement with earlier findings of age-dependent differences in the echolocation calls of big brown bats, we could discriminate calls by age class (juvenile versus adult) with 75% correct classification by DFA. We were not able to separate calls by sex. For discrimination of individuals, we found 63% correct classification (compared with 2.5% expected by chance alone). Correct classification was significantly higher for adults than for juveniles (74% versus 69%), perhaps indicating that calls become more stable as a bat ages.