Background: Strength loss is strongly associated with functional decline and is reversible with exercise. The effect of increased strength on function has not been clearly established. The purpose of this study was to determine whether strength gain is associated with improvement in physical performance and disability. Methods: One hundred functionally impaired community- dwelling men and women (77.6 ± 7.6 yrs) were tested at base-line and outcome for lower extremity strength, physical performance, and disability. After random group assignment, exercise participants received strengthening exercises in their homes three times a week for 10 weeks while control subjects continued their normal activities. Using multiple regression techniques, the relationship between strength gain and improvement in physical performance and disability was assessed, controlling for age, depression, and baseline strength. Results: A significant impact of strength gain on mobility skills (p = .0009) was found. The impact of strength gain on chair rise performance was significant in participants who were more impaired (p = .04). Strength gain was associated with gain in gait speed (p = .02) and in falls efficacy (p = .05), but not with other balance, endurance, or disability measures. Conclusions: Lower extremity strength gain is associated with gains in chair rise performance, gait speed, and in mobility tasks such as gait, transfers, stooping, and stair climbing, but not with improved endurance, balance, or disability. Strength gain is also associated with improvement in confidence in mobility. Factors that may influence the ability of strength gain to affect function are initial level of frailty and specificity of exercise. These results support the idea that strength training is an intervention that can potentially improve physical health status in many frail elders.