This study investigated the gross motor development of children at two day care centers, one with a movement-oriented physical education program and the other with an unstructured free play period. Also studied were the biological factors of age and sex. A total of 146 children were tested during a 3-year period. During the last two years, children at two other centers were tested as a control group. Subjects were given the Test of Gross Motor Development. A motor quotient indicating level of motor ability was derived from locomotor and object control subtests. Findings suggested that: (1) preschool-age children benefit from physical education regardless of teaching styles or curriculum used; (2) the movement-oriented approach produces better results on a motor development test and is an appropriate method of teaching preschool-age children; and (3) there are sex-specific differences in motor skill development at a very early age in both object control and locomotor skills. (RH)