The low-temperature heat capacity of cuprates(La2CuO4,La2−xMxCuO4(M = Sr, Ba)andNd2−xLaxCuO4)is studied in the temperature range 2–45 Kby using pulsed differential calorimetry. It is found that the coefficient of the linear term of heat capacity remains unchanged over the entire temperature interval under investigation. The special role of La atoms in the formation of the anomaly in the acoustic region of the phonon spectrum of these compounds near6 meVis demonstrated. This anomaly is connected with peculiarities in the interaction of these atoms with the environment. ©1997 American Institute of Physics.