Surprisingly little research exists concerning parenting and family life when a parent has a chronic illness. This study expands the existing research base by examining intact families that include a parent diagnosed with multiple sclerosis, using a valid and reliable measure of family functioning to determine differences between families with MS and comparison families, as well as differences in functioning within families with MS. Participant families (who were remarkably similar to the national population with MS) and comparison families completed the Family Assessment Measure - Version III and results were considered as a family unit, and further on the basis of patient gender, illness severity, and time since illness onset. Results indicated that family functioning was negatively impacted by parental MS. However, the impact appears as a less efficient functioning within the range considered normal by the FAM-III, and not as an indication of clinical difficulties in need of intervention. Parents with MS and their families, medical professionals, and researchers interested in family response to illness will find these results valuable in planning treatment and future research.