Purpose: Concentrations of sex steroid hormones--estrogens, progesterone, and testosterone--have been associated with premenstrual and menstrual vocal symptoms. However, the extent to which these symptoms may be reflected on acoustical features of the voice is still debated. This study investigates variations in fundamental frequency (f[subscript o]) and related parameters in connected speech across phases of the menstrual cycle and during the use of a combined oral contraceptive pill (OCP). Method Electrolaryngographic recordings were made, and blood samples were collected at three different phases of the menstrual cycle--menstrual, follicular, and luteal--for placebo and OCP use. These two conditions were blindly and randomly allocated in the study. Speaking f[subscript o] (SFF), SFF standard deviation, SFF rate of change, SFF slope, maximum and minimum f[subscript o], and f[subscript o] range were extracted for nine healthy females while reading a phrase from the Rainbow Passage. Concentrations of sex hormones were analyzed in serum. Nonparametric statistical tests were carried out to assess differences between phases and conditions. Results SFF, its standard deviation, and maximum f[subscript o] were significantly different between phases of the menstrual cycle for placebo use only. Menstrual phase showed the lowest values. Maximum and minimum f[subscript o] were significantly different between placebo and OCP use for menstrual and follicular phases, respectively. Conclusions Fluctuations in sex steroid hormones across the menstrual cycle alter f[subscript o] in speech more than a particular hormonal concentration. OCP use seems to have a stabilizing effect on the voice relative to f[subscript o] and related parameters in speech.