Attachment has generally been examined from the infant's perspective. We focused on mothers' post-partum thoughts and behaviors. Guided by an ethological approach, maternal bonding was examined under conditions of proximity, separation, and potential loss. Ninety-one mothers were interviewed: mothers of full-term infants who maintained continuous proximity to the infant, mothers of healthy premature infants who were separated from the infant, and mothers of very low birthweight infants who experienced potential loss and prolonged separation. Mothers of term infants reported medium-to-high levels of preoccupations with thoughts of infant safety and well-being. Preoccupations increased with separation (Group 2) and significantly decreased with impending loss (Group 3). Attachment behaviors and representations were the highest among mothers of term infants and declined linearly with the duration of mother–infant separation. Maternal trait anxiety and depression were related respectively to higher levels of preoccupations and reduced attachment behaviors and representations, independent of the infant medical condition and mother–child separation. Discussion focused on the comparability of maternal and infant attachment in relation to the neurobiological system underlying bond formation.