The purpose of this study was to cross-sectionally and longitudinally examine the developmental process of search behavior in infancy. Subjects were 23 Japanese normal infants (11 males and 12 females) who were individually tested once a month from the age of six to 13 months in laboratory settings. Small toys and three white opaque cubic boxes were used as hidden objects and covers, respectively. The subjects' spontaneous search behavior was observed after hiding a toy under one of the three boxes on a table. Fixation time to either of the three boxes was measured, and the entire procedure was videotaped. Cross-sectional data revealed the general developmental process of search behavior. Results indicate that the developmental process of search behavior is from nonmanipulation despite fixation to trial and error manipulation and then to goal-orienting manipulation. However, more than half of the subjects fell in a Redundant pattern of development. Males' search levels were significantly higher than females' at 6, 7, 9 and 11 months of age. These findings and additional results were discussed in relation to previous studies on object permanence and general cognitive development in infancy. (Author/RH)