This article provides guidelines for programs to deliver and sustain effective professional development on sheltered instruction to teachers who teach content to English learners. Many content area teachers have not had university coursework on second-language acquisition or the integration of language and content instruction in teacher preparation courses, yet they face students learning a new language at the same time they are studying subjects such as mathematics, science, and social studies. A methodology these teachers can employ is sheltered instruction that incorporates techniques for making content accessible to English learners and develops students' academic English skills. This article offers recommendations for ongoing professional development that includes a mixture of face-to-face workshops, classroom observations and coaching, school-based professional learning communities, and measurement of implementation. The guidelines are illustrated with research practices and findings related to one model of sheltered instruction, known as the Sheltered Instruction Observation Protocol (SIOP) Model. (Contains 2 notes and 2 figures.)