This chapter develops a framework for classifying approaches to conceptualizing and measuring implementation of innovations. It first develops a typology that distinguishes rollout, modification, programmatic and transformation conceptualizations of implementation. The implications of each conceptualization for measurement of implementation are discussed. Following this a classification scheme for implementation measures is presented that distinguishes measures on the basis of their: (a) criterion for success of the implementation; (b) innovation unit; (c) source of data; (d) measurement scale; and (e) level of analysis. Issues related to various measurement choices are discussed along with recommendations for future research and development in the measurement of implementation.