Purpose: Although functional bladder capacity, as expressed by maximum voided volume and other frequency-volume chart parameters, are important determinants of lower urinary tract symptoms, to our knowledge no population based data are available on changes in voided volume. We determined changes in and determinants of voided volume and voiding frequency with advancing age and with time, as measured by frequency-volume charts. Materials and Methods: We performed a longitudinal, population based study in 1,688 men 50 to 78 years old with followup at 2.1, 4.2 and 6.5 years. Data were obtained using frequency-volume charts for maximum, 24-hour and average voided volume, and 24-hour voiding frequency as well as physical and urological measurements, and self-administered questionnaires. We used a linear mixed effect model to determine factors predicting volume changes. Results: Median maximum and average voided volume decreased with time from 400 to 380 and 245 to 240 ml, respectively, and were smaller in older age groups while 24-hour voided volume showed no change. The 24-hour voiding frequency increased with time and with advancing age. Maximum, 24-hour and average voided volumes were positively related to alcohol intake. Maximum and average voided volumes were negatively related to higher age at baseline and the passage of time. Hypertension, diuretics and post-void residual volume were related to higher 24-hour voided volume. Conclusions: In older men maximum and average voided volume show a small but statistically significant decrease with time and with advancing age while 24-hour voided volume does not. Factors predicting the change in maximum or average voided volume are alcohol intake and higher age.