This research investigated factors that influence the implementation levels of evidence-based comprehension strategy instruction (CSI) among K-3 teachers. An explanatory design was chosen to gather and probe the data. Quantitative data were gathered via a mailed survey distributed through a representative sample of the 40 school districts (through a stratified-random selection of teachers) in a state in the Rocky Mountain West. Expectancy-value theory was applied as it affects self-reported levels of teacher implementation of CSI. Both expectancy and value showed significance for predicting self-reported CSI implementation in two multiple regression analyses. Surveys revealed teachers' perceptions of what impedes or supports their sustained implementation of CSI. These findings suggest that increases in school support will also raise teacher CSI implementation levels. (Contains 14 tables.)