This paper examines the role of replication in empirical economic research. It presents the findings of a two-year study that collected programs and data from authors and attempted to replicate their published results. The research provides new and important information about the extent and causes of failures to replicate published results in economics. The findings suggest that inadvertent errors in published empirical articles are a commonplace, rather than a rare, occurence. Copyright 1986 by American Economic Association.