A study of fundamental vocal frequency values in 14 children aged 11 to 25 months, an age period characterized by changes in physiological and linguistic development, is reported. A developmental trend downward in vocal frequencies is traced across a number of previous studies, but is only tentative and is not documented in the age group under consideration. Although the decrease in average frequency can be explained by physical growth, the decrease in frequency variability cannot be explained as easily, especially in this age group. Based on analysis of spontaneous language samples of this study's 14 infants, the hypothesis that developmental decreases in average frequency and frequency inter-utterance variability occur before 3 years of age, and in infants as young as 11 months, is supported. A list of references, a summary of studies of frequency characteristics in children from birth to five years, and individual characteristics and statistical results of the present study are appended. (MSE)