Rulemaking is among the most important and controversial functions perfonned by public agencies. One of the most persistent and serious problems in rulemaking is delay in the issuance of rules. This research examines the factors influencing rulemaking by the Environmental Protection Agency. Theory directs us to legal requirements, bureaucratic elements, and political influences that may influence the passage of time in rulemaking. We develop a number of measures for each of these variables to determine their individual and combined effects on delay in rulemaking. While our models do account for a substantial amount of the variation in the time it takes to issue rules, their performance is erratic and much remains to be explained. Existing theory does offer more important insights into delay in rulemaking but more work is needed to refine important variables and to uncover forces that have yet to be identified.