We examined whether clinical progress ratings on the Monthly Treatment and Progress Summary form (MTPS), an idiographic treatment progress measure, were meaningfully related to changes measured by two separate standardized instruments; the Child and Adolescent Functional Assessment Scale (CAFAS) and the Child and Adolescent Level of Care Utilization System (CALOCUS). Validity coefficients were examined at intake and three-, six-, and nine-month follow-up periods. Samples were selected for each measure and follow-up period from the population of youth receiving services through the Hawaii Child and Adolescent Mental Health Division's (CAMHD) system of care. Significant youth improvement was evident on all three measures across all follow-up intervals. The type of changes measured by the MTPS and CAFAS were more alike over longer follow-up intervals than changes measured by the CALOCUS. The MTPS captures distinct aspects of client change that overlaps somewhat with CAFAS and CALOCUS measures. The MTPS is a brief client-tailored measure that seems to provide valid, sensitive, and nonredundant client specific treatment outcome information that can be collected on a frequent basis within a complex system of care.