This article details the development of an instrument designed to assess the impact of certain environmental stressors in the pediatric intensive care unit (ICU) on parents of hospitalized children. A theoretical framework based on stress theory and developed by the authors provided the framework for this project. This 62-item scale assessing seven dimensions of the PICU environment was developed in three stages. The first phase in the development of the instrument established the sampling domain of the items, supported content validity, conceptualized the dimensions, developed the scaling, and helped support stability over time. In the second phase of the project, the instrument was administered to 165 parents of children recently discharged from four midwestern ICUs to further evaluate reliability and validity. Results of factor analysis, internal consistency reliability, and construct validity analyses were used to revise the instrument. In the third phase of the project, the revised instrument was administered to 510 parents while their children were in one of five pediatric ICUs. Factor analysis provided seven orthogonal, invariant factors. An alpha coefficient of .95 was obtained for the total instrument; subscale coefficients ranged from .72 to .99 providing support for internal consistency and construct validity.