Longitudinal changes were investigated for selected voice source parameters: fundamental frequency (F0), jitter (period perturbation quotient, PPQ), shimmer (amplitude perturbation quotient, APQ) and glottal noise (normalized noise energy, NNE). Acoustic analyses were made on the sustained phonation of the Japanese vowel /a/ of 20 males and 38 females with no laryngeal disease, which were recorded over periods ranging from 10 to 18 years. The longitudinal change of the parameters was evaluated by the statistical t-test, revealing that: 1) strong individuality existed for significant longitudinal changes in the acoustic parameters, 2) F0 falling is a more typical tendency of vocal aging of females than males, while F0 rising, which has been pointed out in the previous reports for males, was not found, 3) shimmer is a more observable indication of vocal aging than jitter, and 4) glottal noise in a high-frequency region tends to increase with aging.