A community sample of 408 heroin users was interviewed about changes in their predominant route of heroin administration. Clear preferences for specific routes of drug administration were evident. Two predominant routes of administration were found: injection (54%) and 'chasing the dragon' (44%). More than a third of the sample had changed their predominant route of administration (a 'transition'). Most commonly, only one transition was reported, from chasing to injecting. However, transition to injection was not inevitable: the majority of 'chasers' had never moved to regular injecting despite often using at high doses for many years. Modelling suggests that many chasers give up heroin without moving to injecting. The results indicate, however, a continuing risk of switching from chasing to injecting for those who continued to use. Women were less likely to move from chasing to injecting. Some heroin users had made the transition from injection to chasing; 28 (16%) of the current chasers had previously been regular heroin injectors. This change in route is less well-known and to our knowledge has not been previously investigated. Multiple transitions in route were uncommon; predominant route of administration, once established appears robust. Harm reduction interventions directed towards changing the risk behaviours of heroin users should take account of the different routes of current administration and the potential for future transitions within continued drug use.