This study addresses two central issues regarding father involvement in dual earner families using infant day care: (1) Which people are with an infant over the course of a day and which perform key child caregiving tasks? and (2) Are structural and emotional factors in the family associated with father involvement? A total of 41 infants from 3 day care centers in Central Pennsylvania were studied. Data were gathered on demographic and background characteristics, structural variables, child care arrangements, family environment, and father involvement. Findings indicated that parents of infants in day care spent almost three-fourths of the infant's waking hours caring for and being with the infant. Fathers spent more time and engaged in more caregiving tasks than in previously reported studies of single earner households. Father involvement was associated not only with the number of hours the child was in day care, but also with measures of the emotional and structural climate of the family. Traditional demographic features such as occupational status and sex of the child were not related to father involvement. It is concluded that the most significant thing about infants in dual earner families is that the structure and operation of their families differs from those of single earner families. (RH)