Epidemiologic studies of adverse events in hospitals generally focus on identifying the incidence of errors and the most common types. This AHRQ-funded study sought to identify underlying work factors that contributed to errors, by soliciting the perspectives of front-line providers. These opinions were obtained by having senior managers directly observe work systems, in a fashion similar to executive walk rounds. Front-line staff most commonly identified equipment problems and facility design problems as major contributors to errors, with staffing and communication issues also mentioned frequently. These human factors issues contribute to latent errors, and the authors suggest that equipment and facility problems deserve more attention in the quest to improve patient safety.