An oscillatory platform can be used as a simple measuring instrument for modelling balancing capacity. We sought (1) to determine the test-retest reliability of the Lehr's damping ratio for characterizing the balancing ability on an unstable oscillatory platform of 20 healthy young and 20 healthy elderly participants and (2) to compare balancing ability on an unstable oscillatory platform between groups. Tests were performed during standing on both limbs and on one limb (dominant or non-dominant). The average of differences of the Lehr's damping ratio was 0.004±0.003 (3.77%±3.89%), and tests conducted at different times showed strong correlations (range 0.978-0.998). The average value of the Lehr's damping ratio was significantly smaller for elderly compared to young participants and it was significantly smaller for participants standing on their non-dominant limb compared to when they stood on both limbs or on the dominant limb. Based on this reproducible measuring method, Lehr's damping ratio depends on lateral dominance, and age.