Background: The organizational context in which nurses practice is important in explaining variation in patient outcomes, but research has been hampered by the absence of instruments to measure organizational attributes empirically. Objectives: To report on the development and utility of the Revised Nursing Work Index (NWI-R) in measuring characteristics of professional nursing practice environments. Methods: The NWI-R was used in a national acquired immunod-eficiency syndrome (AIDS) care study. The sample consisted of 40 units in 20 hospitals. Of these 20 hospitals, 10 provided AIDS care in both dedicated AIDS units and general medical units, thus introducing to the design an element of internal control. The remaining 10 hospitals were selected through a matching procedure. Three of the matched control hospitals were magnet hospitals. Nurses were recruited into the study if they worked at least 16 hours per week on the study unit. The nurses completed the NWI-R in addition to other measures. Results: A response rate of 86% was attained. Response rates per unit ranged from 73% to 100%. Cronbach's alpha was 0.96 for the entire NWI-R, with aggregated subscale alphas of 0.84 to 0.91. Validity of the NWI-R was demonstrated by the origin of the instrument, its ability to differentiate nurses who worked within a professional practice environment from those who did not, and its ability to explain differences in nurse burnout. Conclusion: The NWI-R has been found to capture organizational attributes that characterize professional nursing practice environments.