Measurement of principal implementation behaviors has proved difficult to researchers in educational leadership due to a lack of consensus on the operational definitions of leadership constructs. The Principal Implementation Questionnaire (PIQ) was developed and validated with the intention of providing clarity in the assessment of principal leadership behaviors in the implementation of effective reading programs. Constructs were operationally defined within the context of the population of interest, with subsequent item writing centered around the constructs. A resulting calibration sample of principals from Florida "Reading First" schools was used to test the hypothesized measurement model to determine how well the items were described by the proposed factors. Results from LISREL analyses revealed a well-fitted model, based on numerous fit indices.