The predominant frequency, rate of clucking and intensity of the maternal cluck vocalization of the broody hen (Gallus gallus) are described. The frequency, rate of clucking, and level of intensity of the cluck vocalizations were altered independently of each other. Three-day-old chicks were given a simultaneous choice test between the normal and an altered cluck or between the two altered clucks in a 'T' shaped simultaneous choice test apparatus. No significant preferences were found when the frequency was increased or decreased by 25% (Experiment 1A) but the chicks significantly prefer the normal cluck over a cluck with a 33% increase in frequency. The preference for the normal cluck over the 33% decrease in frequency was nearly significant (Experiment 1B). Thus, there exists an optimal frequency range for the maternal cluck vocalization of the domestic hen. When the rate of clucking was increased or decreased by 25% the chicks preferred the higher rate of clucking in all conditions (Experiment 2). However, the highest rate of clucking used in this experiment was close to that of the normal cluck. When the intensity was increased or decreased by 100% no significant preferences were found in any choice test (Experiment 3). This contrasts with earlier findings possibly due to a methodological difference.