Objectives: Relative and absolute reliability are the important aspects of the test that many clinical decisions are based on them. in many cases, the only basis for the decision is relative reliability while the absolute reliability is also very important. This study aimed to measure and calculate the relative and absolute reliability of Sit To sand-5 repetition.

Methods and Materials: 11 community-dwelling older adults 65 years and older (69.64±3.58) and 20 healthy young in the age range 20 to 35 years (28.80±4.15) using Sit to Stand-5repetition were evaluated twice with an interval of 2 to 5 days.

Results: The "Minimal Detectable Changes" in seniors was 29.5 seconds and Youth 3.02 seconds and "Coefficient of Variation" were 27% and 19% respectively.

Conclusion: The results of this study showed in assessing progress during treatment sessions or judgment about progression or regression, elderly people must more change than young to consider change as a real change not accidentally .