The perinatal mortality rate has decreased in Scotland from 15.4 per 1,000 total births in 1978 to 8.7 per 1,0000 total births in 1989. This improvement is largely accounted for by a decrease in mortality of infants weighing less than 1500g at birth. It has become important to learn more about the nutrition of these infants in an effort to decrease their mortality rate still further, to optimise their ability to combat the diseases of prematurity, and to allow them to achieve their potential in both growth and development. Most infants weighing less than 1500g at birth are unable to establish full oral feeds immediately. Total parenteral nutrition, transpyloric feedings or gastric feedings must be given to provide the infant with adequate calories for growth and development. This thesis contains a study in which very low birthweight infants were randomly allocated to nasoduodenal or nasogastric routes of milk administration. The nasoduodenal route proved to be more complex, more time-consuming, and offered no advantages to the infants. Gastric feedings are recommended as the best method of providing calories enterally to the very low birthweight infant. Rickets of prematurity continues to be described in the 1990's, involving diffuse demineralisation of the skeleton and even bone fractures. Elevation of plasma alkaline phosphatase activity is a commonly used biochemical marker of this condition. Since large doses of vitamin D do not prevent the disease, it may be that the problem is one of substrate deficiency. Included in this thesis is an examination of the effects of adding extra calcium and then extra phosphorus to the milk given to cohorts of very low birthweight infants. The addition of calcium alone reduced radiological evidence of rickets, while the addition of both calcium and phosphorus maintained plasma alkaline phosphatase activity within normal limits throughout the study period.