How do young infants discover word meanings? We have theorized that caregivers educate infants' attention (cf. Gibson, J.J., 1966) by synchronizing the saying of a word with a dynamic gesture displaying the object/referent (Zukow-Goldring, 1997). Detecting an amodal invariant across gesture and speech brackets the word and object within the auditory and visual flow of events and constitutes the basis for perceiving them as belonging together (Zukow-Goldring and Rader, 2001; cf. Spence, 2007). To test the effect of gesture on infant attention and word learning, we presented 9-14-month-old infants with videos of speakers using synchronous dynamic, static, or asynchronous dynamic gestures. We hypothesized that infants would attend more to the object at the time the word was spoken when the gesture was dynamic and synchronous with speech and that this synchrony would result in better word learning. We found that infants looked more at the object at the critical time and displayed better word learning in the dynamic synchronous condition compared with the other gesture conditions. These results highlight the key role that synchronizing word and gesture plays in infants' learning of the correspondence between word and referent. (Contains 3 figures.)