Abstract
The electrolyte concentration of the vitreous humour of the eye in a consecutive series of 40 infants dying unexpectedly at home was measured. In 25 of these infants no morbid anatomical cause of death was found, but in half of these infants analysis of the vitreous humour indicated the presence of hypernatraemia, either with or without uraemia. High solute feeding and water deficiency could therefore have been a major factor in the death of these infants. Estimation of the vitreous electrolytes is an essential part of examination of children falling within the `cot death' group.