The purpose of this qualitative descriptive study was to explore how special education teachers describe selecting and applying differentiated instructional strategies for students with mild, moderate, to severe disabilities in self-contained classrooms within a school district in Arizona. Jean Piaget's social constructivism theory and Carol Ann Tomlinson's differentiation instructional framework was used as the theoretical framework to understand differentiated instruction within a special need's classroom. Two research questions guided the study: (1) How do special education teachers describe selecting differentiated instructional strategies for students with mild, moderate, to severe disabilities in self-contained classrooms? (2) How do special education teachers describe applying differentiated instructional strategies for students with mild, moderate, to severe disabilities in self-contained classrooms? Ten K-8th grade self-contained special education teachers within the state of Arizona participated in the study. One-on-one semi-structured interviews and teachers' reflective journals were used to collect data. A thematic analysis was used to analyze the data. Five themes emerged and each participant would spend time: (a) interpreting individual educational plans for each individual student; (b) administering formal and informal assessments; (c) observing each individual students' behavior socially and academically; (d) comparing grade-level standards to student readiness levels and scaffolding assignments accordingly; (e) progress monitoring each student as they navigate through a structured classroom routine. The results of the study indicated that the implementation of differentiated instruction should be scaffolded according to each student's readiness level. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]