Objective: This study tested a 'wise' intervention (quick prompt of a specific psychological mec) in acute care hospital units to improve nurses' hand hygiene compliance (HHC). Design: A multiple baseline design in two medical-surgical teaching hospitals in the United States. Measurements: Hand hygiene data was collected using an electronic compliance monitoring system with sensors placed in doorways and on corresponding soap and alcohol-based hand rub dispensers. The outcome measure was the proportion of opportunities in which HH was undertaken by staff per week in each unit. Intervention: A quick-and-easy psychological prime to reinvigorate professional identity. Methods: Interrupted time series analysis using a quasi-Poisson regression model with statistical process control charts for each unit. Results: A statistically significant increase in HHC rates that was sustained for months post-intervention. However, the patterns by unit were not statistically significant once temporal trends were considered. Other factors, such as the unit type and the use of incentives could have impacted the results. Conclusions: These analyses suggest that the aggregate impact should not be taken as evidence of intervention effectiveness. This study therefore cannot be considered to have provided a strong foundation for use of a 'wise' intervention, despite its relatively small financial, logistical and psychological cost.