Currently, developmental psychologists rely on paradigms that use infants' looking behavior as the primary measure. Despite hundreds of studies describing infants' visual exploration of experimental stimuli, researchers know little about where infants look during everyday interactions. Head-mounted eye-trackers have provided many insights into natural vision in adults, but methods and equipment that work well with adults are not suitable for infants-the equipment is prohibitively big and calibration procedures too demanding. We outline the first method for studying mobile infants' visual behavior during natural interactions. We used a new, specially designed head-mounted eye-tracker to record 6 infants' gaze as they played with mothers in a room full of toys and obstacles. Using this method, we measured how infants employed gaze while navigating obstacles, manipulating objects, and interacting with mothers. Results revealed new insights into visually guided locomotor and manual action and social interaction.