Abstract. Poultry scientists and researchers have been studying the possibility of identifying bird stress from the vocal patterns of broiler i¬‚ocks. Being able to identify stress or sickness in a i¬‚ock can lead to early interventions. However, as the i¬‚ock ages, the vocal properties change. This paper presents the preliminary results of an age classii¬cation technique using the C4.5 decision three algorithm using Mel-frequency cepstral coefi¬cients (MFCCs), audio frequencies commonly used from speech processing. Sound data was collected continuously over a 61-day period. The i¬‚ock was composed of 400 Cobb500TM broilers raised under research conditions mimicking commercial operations. Results of the data processing and the C4.5 classii¬cation indicate that age can be determined within one day of error with 70% frequency. This process of determining age of a i¬‚ock is intended to be the i¬rst step in a larger comprehensive system for identifying the condition of the i¬‚ock and assessing animal welfare.