Because unemployment benefit reforms typically package together a number of changes, few existing evaluations have been able to isolate the effects of changes in job search monitoring intensity on benefit recipient stocks or flows. Those few studies that do so draw mixed conclusions. This paper provides new estimates of monitoring impacts by exploiting plausibly exogenous periods where search monitoring has been temporarily withdrawn - with the regime otherwise unchanged - during a series of benefit office refurbishments in Northern Ireland. As we would expect from search theory, withdrawal of monitoring significantly increases the stock of unemployment benefit recipients via reduced outflows. © The London School of Economics and Political Science 2008.