This book presents a study of co-offering relations among youths under twenty-one suspected of criminal offences in Stockholm during 1991–5. In total, the study includes just over 22,000 individuals suspected of around 29,000 offences. Jerzy Sarnecki employs the methods of network analysis which makes it possible to study the ties, social bonds, interactions, differential associations and connections that are central to many of the sociologically oriented theories on the aetiology of crime. Up to now, network analysis has been used only rarely in the criminological context. The book discusses many aspects of Stockholm's delinquent networks such as the existence of delinquent gangs and a criminal underworld, the durability of delinquent relations, and the choice of co-offenders with respect to sex, age, residential location, ethnic background and earlier delinquent experience. It also considers the effects of societal intervention on criminal networks. This unique study will appeal to a wide audience.