OBJECTIVE: To determine the percent reduction cutoffs on the Multidimensional Anxiety Scale for Children (MASC) that optimally predict treatment response and remission in youth with anxiety disorders. METHOD: Youths and their parents completed the MASC-C/P before and after treatment, and the Anxiety Disorders Interview Schedule for DSM-IV-Child and Parent Versions (ADIS-IV-C/P) and the Clinical Global Impression-Improvement Scale (CGI-I) were administered by independent evaluators. Treatment response and remission were defined by post-treatment ratings on the CGI-I and the ADIS-IV-C/P, respectively. Quality receiver operating characteristic methods determined the optimal cutoff on the MASC-P for predicting overall remission (loss of all study entry diagnoses) and optimal percent reductions on the MASC-P for predicting treatment response and remission of separation anxiety, social anxiety, and generalized anxiety. RESULTS: A post-treatment raw score of 42 optimally predicted remission. A reduction of 35% on the total MASC-P predicted treatment response. A reduction of 30% on the Separation Anxiety/Panic subscale of the MASC-P predicted separation anxiety remission. A reduction of 35% on the Social Anxiety subscale of the MASC-P predicted social anxiety remission. The MASC did not evidence a cutoff for remission of generalized anxiety disorder. CONCLUSION: MASC cutoffs can facilitate comparison across studies and guide practice, aiding clinicians in assessing progress and informing treatment plans.