When frail older people become acutely ill, they are at increased risk of further functional deterioration and rehabilitation is needed to restore functioning. The effects of an out-patient multicomponent training program including strength training after hospitalization were studied in a randomized controlled trial. Sixty-eight women (mean age 83.0 +/- 3.9 years) who were hospitalized due to an acute illness and were mobility impaired at admission were randomized into training (N = 34) and home exercise (N = 34) groups. Maximal voluntary isometric strength of knee extension and hip abduction, dynamic balance, and maximal walking speed were measured before and after the 10-week training period, and 3 and 9 months after the end of the intervention. After the intervention, significant improvements were observed in the training group compared to the home exercise group in the maximal voluntary isometric knee extension strength (20.8% vs. 5.1%, P= 0.009), balance scale (+ 4.4 points vs. -1.3 points, P= 0.001) and walking speed (+ 0.12 m s-1 vs. -0.05 m s-1, P= 0.022). Effects on knee extension and hip abduction strength, balance and walking speed were observed 3 months later, and some effects on hip abduction strength (9.0% vs. -11.8%, P= 0.004) and mobility were still apparent even 9 months after the intervention.