The purpose of this project aims at standardizing the Motor Scale of Bayley Scales of Infant Development, establishing age norms for Chinese infants and toddlers and understanding the major characteristics of motor development of infants and toddlers. These knowledge can be for infant caring and clinical diagnosis. The subjects of this study were 1680 infant and toddlers chosen from the northern, central, southern and eastern parts of Taiwan according to their age, sex, maternal education and residence. They were divided into 14 age groups from two to thirty month old. Each subject had been given the motor scale of Bayley Scales of Infant Development. The main finding were as follows: (1) The rate of passing each item in the Motor Scale of Bayley Scales of Infant Development of the subject increased along with age. (2) The motor scores of the subject increased with their age according to a linear tendency. (3) There was no significant differences between female and male subjects in their motor score. (4) Birth order of the subjects, education and occupation of fathers were found to be the important factors to influence the motor development of subjects. Family pattern, education and occupation of mothers and ways of caring infant had no effects on the motor scores of the subject. (5) The Chinese and American subjects had shown the similar growth pattern of their motor development, but the average mean motor raw score was slightly higher for Chinese subject than that of the American subjects. (6) There was a significant positive corelation between the motor and mental development of the subject.