Analysis of medication errors can lead to system improvement and reduced risk only if the errors are detected, reported, and used to design better patient-care practices and systems. Voluntary medication error reporting systems rely on the ability and willingness of individual physicians, pharmacists, and nurses to detect and report errors as part of their routine practice. Because of the central role nurses play in medication administration, it is important to understand their perceptions of the medication error reporting process. This paper describes the development and validation of a survey designed to measure nurse perceptions of medication administration error (MAE) reporting. The survey contains questions in three general content areas: why medication errors occur; reasons why medication errors are not reported; and the estimated percentage of medication errors actually reported. Over the past 10 years, the MAE survey has been administered four times to nurses in Iowa's acute care hospitals statewide. Principal components exploratory-factor analysis with orthogonal rotation was used to determine if the individual items could be combined into subscales. Five subscales emerged for “reasons why MAE occur”; four subscales emerged for “reasons why MAE are not reported.” Subscale reliability was assessed using Cronbach's Coefficient Alpha. Although health care organizations have implemented continuous quality improvement programs that focus on systems, rather than individuals, barriers remain in MAE reporting. Surveys, such as the one described here, provide a basis to begin discussions about improving the system.