The purpose of this mixed-method study was (1) to identify positive and negative deviance cases of implementation fidelity (ie, those who do well and those who do poorly at embracing EBPs integrated in the child care setting) using quantitative fidelity data from a previous implementation of WISE and (2) to explore barriers and facilitators to fidelity through qualitative interviews with deviant cases. This study illustrates methods, applications of theory, and potentially salient constructs that may inform other implementation efforts as well. (author abstract)