Found moderate stability in the classification of maternal adjustment in two longitudinal studies of mothers of children and adolescents with cystic fibrosis and sickle cell disease. In terms of the transactional stress and coping model, stable poor maternal adjustment was associated with higher levels of appraisal of daily stress and palliative coping and low levels of family supportiveness. With initial levels of maternal adjustment, demographic parameters, and follow-up interval controlled, concurrent levels of daily stress accounted for significant portions of variance in maternal adjustment at follow-up for both illness groups. In addition, illness severity, child psychological adjustment, and family conflict added significant increments to maternal adjustment at follow-up in the cystic fibrosis group. Findings are discussed in terms of a basis for subsequent intervention studies to enhance the adjustment of mothers of children with chronic illness.