Tobacco use in the United States is the single most preventable cause of death and disease. The Centers for Disease Control and Prevention's Office on Smoking and Health (CDC/OSH) created the National Tobacco Control Program (NTCP) to foster and support coordinated, nationwide, state-based activities to advance its mission to reduce disease, disability, and death related to tobacco use. CDC/OSH has identified four program goal areas: Preventing initiation of tobacco use among young people; Eliminating nonsmokers' exposure to secondhand smoke; Promoting quitting among adults and young people; and Identifying and eliminating tobacco-related disparities. To determine the effectiveness of NTCP programs, both their implementation and their outcomes must be measured. This manual is intended to provide process evaluation technical assistance to OSH staff, grantees and partners. It defines process evaluation and describes the rationale, benefits, key data collection components, and program evaluation management procedures. It also discusses how process evaluation links with outcome evaluation and fits within an overall approach to evaluating comprehensive tobacco control programs. Previous CDC initiatives have provided resources for designing outcome evaluations. This manual complements CDC's approach to outcome evaluation by focusing on process evaluation as a way to document and measure implementation of NTCP programs. The content of this manual reflects the priorities of CDC/OSH for program monitoring and evaluation, and augments two other CDC/OSH publications: Key Outcome Indicators for Evaluating Comprehensive Tobacco Control Programs and Introduction to Program Evaluation for Comprehensive Tobacco Control Programs. This manual: Provides a framework for understanding the links between inputs, activities, and outputs and for assessing how these relate to outcomes; and Can assist state and federal program managers and evaluation staff with the design and implementation of process evaluations that will provide valid, reliable evidence of progress achieved through their tobacco control efforts.