This study's purpose was to investigate whether a 10-week low-intensity strength-training program could improve strength of the knee extensors and functional ability. Participants 65 years and older with low knee-extensor muscle strength were randomized into an exercise (n = 11) and a control group (n = 10). Knee-extensor strength and functional ability were measured before and after the program and again 6 months later. Knee-extensor strength (Nm) increased by 54% (13% in the control) by the end of the training program (F = 13.02, p = .01), and most of this improvement was still present 6 months later. The program had a beneficial effect on functional tasks, especially the time taken to rise from a chair in combination with a 3-m walk (F = 3.99, p = .03) and self-reported ability related to lower extremity performance (F = 6.97, p = .02). It seems that this program could contribute to improving functional ability in frail older people.