In agreement with the new paradigm of supports, this study examines the adequacy and psychometric properties of the Supports Intensity Scale (SIS) in a sample of 182 participants with severe mental illness (mean Global Assessment of Functioning [GAF] score = 60.2). The measure focuses on identifying the profile and intensities of support needs and on the planning and service delivery rather than on weaknesses and limitations. Internal consistency indexes ranged from .83 to .97; interrater reliability indexes ranged from .67 to .98. Intercorrelations among SIS subscales supported its construct validity. SIS scores correlated to GAF scores and length of disease. Discriminant analysis correctly classified 60.9% of participants. Therefore, the SIS demonstrated adequate reliability and validity, and it can be used by nursing professionals to plan for required supports in this population.