Abstract Evaluation of therapeutic results and of the efficacy and effectiveness of treatments is an area of interest both for clinicians and researchers. In general, randomized controlled trial designs have been used as the methodology of choice in which intergroup comparisons are made having a minimum of participants in each arm of treatment. However, these procedures are seldom used in daily clinical practice. Despite this fact, the evaluation of treatment results for a specific patient is important for the clinician in order to address if therapeutic goals have been accomplished both in terms of statistical significance and clinical meaningfulness. The methodology based on the reliable change index (Jacobson y Truax)1 provides an estimate of these two criteria. The goal of this article is to propose a procedure to apply the methodology with a single case study of a woman diagnosed with major depression and treated with electroconvulsive therapy.