Support of aging parents is usually credited to daughters. To investigate the nature of support provided by sons and daughters to married or widowed mothers, married and widowed mothers from the 1977 Social Security Administration's Midwestern Retirement Community Study listed important people and details of the support (emotional, social, and instrumental) received by and given to each of these primary relations. Analysis of the data compared sex of adult children with marital status of mother, and sex of adult children with reciprocity of supportive relationship. The results showed only small support differentials between the sons and daughters of married mothers. In the absence of face-to-face contact, mothers heard slightly more from their daughters than from their sons. There was no significant difference in the amount of support given by sons and daughters. For the widowed mother, the daughter was the greater supporter in both face-to-face and the absence of face-to-face contacts. The widowed mother received more social and instrumental (task-oriented) support from her daughter. Both sons and daughters gave more social support to their widowed mothers than they received from them. Both sons and daughters were more likely to give instrumental support to widowed rather than married mothers. (BL)