This study measured infant responses to mother and stranger as a function of mother and stranger distance. A group of 10-month-old infants were pretested for level of object permanence and person permanence, and 18 males and 18 females were chosen as study participants. The infants were randomly assigned to one of three treatment groups: (1) stranger near, (2) stranger far, or (3) stranger absent. In each treatment group, there were three 5-minute trials with the mother near, far, and absent. Observations of the infant (proximity to mother and stranger, fussing, crying, and playing with a novel toy) were made by the experimenter, who was concealed behind a wooden partition set up in the infant's living room. The results indicated that stranger distance from the infants was unrelated to their behavior but that both mother distance and trial number had significant effects. As mother-infant distance increased, babies fussed sooner and longer, and played less with the novel toys. As the trial number increased, the infants crawled to their mothers earlier in the trial, fussed sooner, and played less with the novel toy. These findings were interpreted as supporting Bowlby's contention that attachment behavior is related to the degree of maternal accessibility. (JMB)