After summarizing the development of electronic monitoring as a penal measure in England and Wales and elsewhere, the article presents the main findings of evaluative research on pilots of restriction of liberty orders with electronic monitoring in three Sheriff Courts in Scotland. The evaluation found that fewer orders were made than the contractors who supplied the equipment had expected, and that it was rare for orders to be completed without some breach of their requirements. Younger offenders, and those with serious criminal records, were less likely to complete orders successfully. Although there was no consensus about the types of offence or offender for whom the orders were most suitable, they were generally imposed on young men for whom the alternative would have been a custodial sentence or another high-tariff community penalty. It was estimated that the orders replaced custody in about 40 per cent of cases, but they would only produce a cost saving if the sentences they replaced were relatively long. Offenders and their families generally welcomed the orders, since they believed them to be alternatives to custody. The policy implications of the research are discussed, in the context of more general reflections on the issues raised by electronic tagging.