Restricted and repetitive behaviors (RRBs) are a core feature of autism spectrum disorders. They constitute a major barrier to learning and social adaptation, but research on their definition, cause, and capacity for change has been relatively neglected. The last decade of research has brought new measurement techniques that have improved the description of RRBs. Research has also identified distinctive subtypes of RRBs in autism spectrum disorders. Research on potential causal origins and immediate triggers for RRBs is still at an early stage. However, promising new ideas and evidence are emerging from neurobiology and developmental psychology that identify neural adaptation, lack of environmental stimulation, arousal, and adaptive functions as key factors for the onset and maintenance of RRBs. Further research is needed to understand how these factors interact with each other to create and sustain atypical levels of RRB. The literature indicates that RRBs have the potential to spontaneously reduce across time, and this is enhanced for those with increased age and cognitive and language ability. Research on interventions is sparse. Pharmacological treatments can be helpful in some children but have adverse side effects. Behavioral intervention methods provide the better intervention option with positive effects, but a more systematic and targeted approach is urgently needed. Evidence suggests that we will learn best from the last decade of research by taking a developmental perspective, by directing future research toward subtypes of RRBs, and by implementing early intervention targeted to improve RRBs before these behaviors become entrenched. (Contains 1 table and 1 footnote.)