The objective of this longitudinal study is to explore the relationship between temperament and physical development among infants in Beijing, China. A total of 1117 term, normal and singleton infants were followed regularly for 12 months. Body weight and horizontal length were measured at 42 days and monthly from the third to twelfth month of their lives. Infants' temperament was assessed using the revised Chinese infants' temperament scale when the infants were 6 months. There was a significant difference on temperament dimensions between infants' genders (P < 0.05). Infants' weight and length were significantly related to their parents' weight and height. Infants with positive temperaments (easy and intermediate) were heavier than those with negative temperaments (difficult and slow to warm up) (P < 0.05). The horizontal length of boys was related to their temperament categories (P < 0.05). Infants' weight and length were significantly related to their temperament category and parents' weight and height.