Mothers' actions are more enthusiastic, simple, and repetitive when demonstrating novel object properties to their infants than to adults, a behavioral modification called "infant-directed action" by Brand and colleagues (2002). The current study tested whether fathers also tailor their behavior when interacting with infants and whether this modification differs from the infant-directed action that mothers show. A sample of 42 parents (21 mothers and 21 fathers) demonstrated the properties of two novel toys to their infants (12-month-olds) and to other adults. Fathers and mothers modified their actions with respect to repetitiveness, rate, range of motion, proximity, interactiveness, and enthusiasm compared with interactions with other adults. Fathers differed from mothers with respect to proximity, carrying out actions closer to their infants than mothers did. These results provide evidence that fathers show modifications in their infant-directed action that is similar to that of mothers. (Contains 4 figures and 3 tables.)