Self-produced locomotion is regarded as a setting event for other developmental transitions in infancy with important implications for socioemotional development and parent-child interaction. Using an age-held-constant design, this study examined changes in reported infant behaviour and maternal proactive/reactive control and compared them with direct observations of infant and maternal behaviour associated with the development of self-produced locomotion. Maternal reports were obtained prior to the locomotor transition and, for half the sample, after infants had transitioned to effective mobility. Observations of all infants were conducted shortly after the second interview. Prelocomotor and transitioning infants showed none of the expected behavioural differences (e.g. emotionality and compliance) associated with the locomotor transition. There was modest confirmation of expected differences in maternal behaviour, particularly in the use of reactive control techniques, and mothers of transitioning infants showed higher proactive controls before their infants began to crawl. These findings suggest that the changes in parent-child interaction associated with the locomotor transition may have as much to do with parental expectations than with changes in infant socioemotional behaviour. (Contains 3 tables.)