The development of speech was studied among three groups of babies. The first group, i. e. the children who were in the care of the Establishment in the years 1957—1958, was appraised retrospectively on the basis of an analysis of 100 detailed records about their development of speech. The second group include children from the same Establishment from five to twelve months old, who were given special care far beyond the usual possibilities of the Establishment. This group was followed longitudinally. The third group was made up of fifteen children coming from the family environment. The author proves on the basis of this material that a child begins to understand speech when 28 weeks old. She lays down criteria for understanding the speech of children in the Establishment for each month of their age of development both as to quality and quantity (a quantitative as well as qualitative index). She stresses the significance of emotions for the development of the child’s speech. By means of examples of two sub-groups of the second group of children with totally different individual peculiarities of the higher nervous activity the author proves that the development of speech is closely connected with the child’s ability to adapt itself to new faces, new environment, and new situations. A baby’s vocabulary is attached.