Introduction to the TEC Special Issue on Data -Based Individualization by Louis Danielson and Celia Rosenquist. Teaching Exceptional Children, Vol 46, No. 4. This article is about the ongoing work of the National Center on Intensive Intervention (NCII: www.intensiveintervention.org). NCII’s appraoch to intensive intervention is based on concepts from data-based individualization (DBI) which is a systematic method for using assessment data to understand when and how to intensify instruction in reading, math and/or behavior. DBI is a process and not a single program and links intervention as well as assessment over time. When using a DBI, staff must adapt and individualize interventions when needed. The elements of DBI include determining a seconday intervention program, progress monitoring, diagnostic assessment, intervention adaptations and more progress monitoring. There is not one specific program or method that is used as progress monitoring will determine if the program used is working. If it is not working, staff must be willing to adapt and change strategies. Progress is monitored over several weeks or more.