Abstract
The objective of this article was to develop and psychometrically evaluate a self-report instrument that would assess interpersonal influence in families. The Influence in Families Questionnaire (IFQ) was developed as a 16-item scale which assesses both positive and negative influence. The IFQ and its subscales, when administered to a sample of 581 adolescents and young adults, showed high internal consistency and exhibited a promising pattern of convergent, divergent and criterion validity in relation to relevant criteria such as impact messages, family and attachment relationships and interpersonal sense of control. Overall, these results suggest that the IFQ is a useful instrument for measuring interpersonal influence within families.