The issue of "Yobiyose-rojin," elderly parents relocated to the home of one of their children because of the care required by their physical and mental conditions, has been the subject of recent attention in Japan. To determine the effective assistance that caregivers require, the authors compared daughters with daughters-in-law who care for an elderly parent in terms of characteristics and factors that might contribute to the caregiver's burden. Daughters-in-law perceived a much stronger burden although they took care of a less-impaired parent for fewer hours a day than daughters. The results indicated that an appropriate form of support must be carefully chosen based on the identity of the primary caregiver.