Objectives: This study investigated the gender and age differential effect of major chronic diseases on activity of daily living (ADL) disability. Methods: Surveyfreq and Surveylogistic regression analyses were employed on the 2005 Korean National Health and Nutrition Examination Survey (KNHANES) with a sample of 3,609 persons aged 65 - 89. Results: After adjusting for potential covariates, stroke, among elderly men more so than women, had a 2-3 times greater odds of engendering ADL disability in the 65-69 (p < 0.05) and 70-79 age groups (p < 0.01). In comparison to elderly women, cancer, diabetes, and incontinence in elderly men was associated with a higher risk of ADL disability in the 70 - 79 age group (p < 0.05), and this association was also observed for pulmonary disease in the 80-89 age group. Among elderly women, however, a significant association between incontinence and ADL disability was identified in all three age groups. In addition, this association was found in pulmonary disease and diabetes in elderly women aged 70 - 79 years. Significant gender differences were observed in the association between stroke in the 60 - 79 age group and cancer in the 70 - 79 age group. Conclusions: Age and gender differences were observed in the effect of chronic diseases on ADL disability.