This paper investigates the sources for regulatory delay in bureaucratic decision making, testing regulatory capture, congressional dominance, and bureaucratic discretion theories of agency behavior. The empirical context concerns relicenses issued by the Federal Energy Regulatory Commission (FERC) for hydroelectric dams, which have taken anywhere from just ten months to over sixteen years to be issued. The reasons for this heterogeneity in regulatory processing times can be expected to be varied and numerous and indeed we find evidence that outside interest groups, the legislature, and bureaucratic discretion are all significant in affecting regulatory processing times. Our most intriguing results concern the effects of environmental interest groups, which, despite their apparent benefit/cost motivation to hasten the relicensing process (independent of relicensing outcomes), overall end up slowing it down.