This study examines 4-year-olds' ability to search and find a missing object, a complex problem-solving task dependent on remembering events, logically deducing the possible subset of hiding places, and implementing situation-dependent search strategies. Sixty-four children recruited from two day care centers in a small midwestern city searched for a lost object on two occasions. On the first occasion, half of the children searched a three dimensional table-top model for a missing item after watching a sequence in which a puppet lost the item. The other children searched under naturalistic conditions, looking in a familiar environment for an object that had been lost while they put away some toys. Half the children were questioned about their search behaviors, after which all children participated in the second search task--a table-top search. In the first task, more searches took place in locations bounded by the last place the object was seen and the first place in which it was discovered missing if children searched in the naturalistic rather than the table top condition. In the second task, children searched the "critical area" more often if they were queried about their search behavior in the first task or if they searched intially in the naturalistic task. The results are discussed in terms of factors affecting the development of problem-solving competence. Three pages of references and tables of data are included. (DR)