['To explore the predictors of treatment effectiveness for women with urinary incontinence (UI) receiving pelvic floor muscle (PFM) strengthening.', 'Four-month cohort study.', 'Laboratory.', 'Volunteers (N=68; mean age ± SD, 50.5±6.0y) with UI.', 'Four-month daily PFM strengthening exercise program at home.', "Outcome measures included self-reported improvement, Severity Index score, 3-days diary, strength of PFM, and quality of life. The participants' recall of the amount of exercise after the 4-month exercise period was used to assess the exercise adherence.", 'Fifty-one (75%) of 68 women reported that their condition improved after 4 months of exercise. There were significant reductions in Severity Index score, number of voidings per day, number of leakages per day, and impact on quality of life (P<.05). In addition, the score of PFM strength was significantly improved (P=.001). There were no significant correlations between the change score of the Severity Index and age, body mass index, parity, type of UI, duration of UI, menopausal status, and amount of exercise (all P>.10). Multiple regression analysis revealed that initial severity of symptoms and improvement of PFM strength predicted 51.3% of variance in 4-month exercise effectiveness (change score of the Severity Index).'] Is exercise adherence to pelvic floor muscle strengthening a significant predictor of symptom reduction for women with urinary incontinence?