A series of stranger sexual assaults poses considerable obstacles for law enforcement officials. One such preoccupation is concerned with whether or not the offender will escalate in the severity of his behaviours with subsequent victims. The current study uses transition matrices to address whether or not the offending patterns of 72 serial stranger sex offenders change from one victim to the next as it pertains to their sexual acts and level of physical force used during the crime. Findings indicate that stability, specifically the offender's intrusive sexual acts and use of physical force, and versatility are present in this sample's offending patterns. To explain changes in offending patterns between victims, multinomial regression analyses indicate that situational factors and modus operandi strategies are important considerations. Implications for investigations are discussed. Copyright © 2013 John Wiley & Sons, Ltd.