Measuring lower body strength is critical in evaluating the functional performance of older adults. The purpose of this study was to assess the test-retest reliability and the criterion-related and construct validity of a 30-s chair stand as a measure of lower body strength in adults over the age of 60 years. Seventy-six community-dwelling older adults (M age = 70.5 years) volunteered to participate in the study, which involved performing two 30-s chair-stand tests and two maximum leg-press tests, each conducted on separate days 2-5 days apart. Test-retest intraclass correlations of .84 for men and .92 for women, utilizing one-way analysis of variance procedures appropriate for a single trial, together with a nonsignificant change in scores from Day 1 testing to Day 2, indicate that the 30-s chair stand has good stability reliability. A moderately high correlation between chair-stand performance and maximum weight-adjusted leg-press performance for both men and women (r = .78 and .71, respectively) supports the criterion-related validity of the chair stand as a measure of lower body strength. Construct (or discriminant) validity of the chair stand was demonstrated by the test's ability to detect differences between various age and physical activity level groups. As expected, chair-stand performance decreased significantly across age groups in decades--from the 60s to the 70s to the 80s (p < .01) and was significantly lower for low-active participants than for high-active participants (p < .0001). It was concluded that the 30-s chair stand provides a reasonably reliable and valid indicator of lower body strength in generally active, community-dwelling older adults.