This article examines the nature and correlates of stress in mothers of children with Down syndrome. In the first part of our study, we compared 27 mothers of children with Down syndrome with 15 mothers of children with heterogeneous causes of learning difficulty. Using Abidin's (1995) Parenting Stress Index (PSI), mothers in the Down syndrome group reported lower total child-related stress levels, particularly concerning the degree to which the mother considers the child acceptable and reinforcing. In the second part, we identified predictors of stress in mothers of children and adolescents with Down syndrome (N = 37). Children's behaviour problems related to higher levels of overall and specific domains of child-related stress, and children who were reported as being more cheerful and outgoing had parents who judged their offspring as more acceptable and reinforcing. Mothers also rated their children as less reinforcing when offspring were older.