ASSESSING THE WITHIN-TRIAL TREATMENT INTEGRITY OF DISCRETE-TRIAL TEACHING PROGRAMS USING SEQUENTIAL ANALYSIS Denys Brand*, Oliver C. Mudford, Angela Arnold-Saritepe and Douglas Elliffe University of Auckland, Auckland, New Zealand Discrete-trial teaching is a strategy frequently used to teach functional skills to individuals with de- velopmental and intellectual disabilities. Research has shown that the within-trial components of the procedure should be administered with ≥90% treatment integrity to facilitate optimal learning. Usually within-trial treatment integrity is measured using whole-session methods such as percentage of trials correctly administered. This study demonstrated one-step Markov transition matrices as a method of assessing within-trial treatment integrity. All components of discrete trials were coded and time- stamped from video recordings of therapist–learner dyads in their typical setting (home or school). Sev- eral types of within-trial treatment integrity errors were identified using the Markov transition matrices, error sequences that could not be identified using a percentage correct analysis. Better identification of errors has the potential both to enhance treatment integrity and to gain efficiency by targeted retraining of therapists. Copyright © 2016 John Wiley & Sons, Ltd. Discrete trial teaching (DTT) is a strategy frequently used to teach functional skills to individuals with developmental and intellectual disabilities. DTT is a critical com- ponent of early intensive behavioral intervention programs. Most skills taught during the initial stages of early intensive behavioral intervention use a DTT format. DTT consists of five distinct within-trial components (Koegel, Russo, & Rincover, 1977). These components are the discriminative stimulus (S D ), a prompt if necessary, a response (correct, incorrect, or no response), a consequence determined by the type of learner response, and an intertrial interval (ITI). Discrete teaching trials have a distinct beginning and end. The presentation of the S D constitutes the beginning of the trial and the start of the ITI the end. In the early stages of teaching, DTT takes place in a structured and controlled environment consisting of one-to-one teaching sessions between therapists and learners. DTT involves breaking down particular skills into smaller parts and teaching each one of these smaller skills individually. *Correspondence to: Denys Brand, 4001 Dole Human Development Center, 1000 Sunnyside Avenue, Department of Applied Behavioral Science, University of Kansas, Lawrence, KS 66045, USA. E-mail: denys.brand@ku.edu Copyright © 2016 John Wiley & Sons, Ltd. Behavioral Interventions Behav. Intervent. 32: 54–69 (2017) Published online 15 July 2016 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/bin.1455