There has been a growing popularity and success rate of balance rehabilitation programs, and this success is paralleled by the growth of technology, making available instruments that provide objective, quantitative, and immediate results. The Balance Master is such a commercially available instrument, consisting of a dual-force platform connected to a micro-computer that provides visual feedback of the centre of gravity (COG) in relation to the theoretical limits of stability. Spontaneous body sway can be measured in a static central position, or in peripheral positions around the limits of stability (peripheral sway area). The trajectory between targets can also be analyzed in terms of time (transition time) and accuracy (path error) of transition, which gives a quantitative measure of dynamic movement of the COG. This study examined the practice effect that occurs while using this instrument over repeated sessions for two schedules of training (daily and weekly) and over two age groups (20-35 years, and 60-75 years). Each group completed a series of postural exercises, with an assessment of static and dynamic postural variables before and after training, and at approximately 3 and 6 weeks post-training. Spontaneous body sway was measured with eyes open, eyes closed, and with visual feedback of the COG. No significant changes were observed in these variables as measured over the four standard assessment occasions. Peripheral sway area and path error decreased significantly for both the daily and weekly training groups from pre- to post-training, and these skills were retained over both retention tests, whereas the tendency toward decreasing transition time was not significant.(ABSTRACT TRUNCATED AT 250 WORDS)