This study examined associations between protein intake, serum insulin-like growth factor (IFG)-1, and height in healthy 2.5 year old children. Multiple forms of protein were compared, including milk, meat, and vegetable protein. Height was positively associated with milk intake but not meat or vegetable protein. IGF-1 was positively associated with milk intake but not meat or vegetable protein. An increase in milk intake from 200 to 600 mL/d corresponded to a 30% increase in circulating IGF-I. This suggests that milk compounds have a stimulating effect on IGF-I concentrations and, thereby, on growth.