Technical Abstract: Background Maximal voluntary muscle strength (MVMS) and leg power are important measures of physical function in older adults. We hypothesized that performing these measures twice within 7-10 days would demonstrate a >5% increase due to learning and familiarization of the testing procedures. Methods Data were collected from three studies in older adult men (60-87 yrs) and divided into two cohorts defined by site and type of exercise equipment. MVMS was assessed in 116 subjects using the onerepetition maximum method at pre-entry (test) and baseline (retest) visits for the chest press, latissimus pulldown, leg press, leg flexion, leg extension exercises and unilateral leg extension power. Results Test-retest scores were not different and did not exceed 0.8 +/- 9.0% in Cohort 1 or 2.3 +/- 9.8% in Cohort 2, except for leg extension which improved by 6.6 +/- 14.4% (p<0.009) and 3.4 +/- 6.8% (p<0.016), respectively. Repeat tests were closely correlated with initial tests (all p<0.001). Pearson correlation coefficients ranged from 0.74 for leg extension power to 0.96 for leg press. Coefficients of variation were <10% (4.2-9.0%) for all exercises except for leg extension power which was 15.5%. Conclusions These findings suggest that it may not be necessary to perform multiple baseline measures to eliminate or minimize potential test-retest improvement as a result of familiarization and learning of the testing procedures with the exception of the leg extension exercises. Moreover, these findings were similar between two study sites using different equipment, which further supports the reliability of MVMS and power testing in older adult men.