The goal of the research was to point out the importance of early prespeech therapy for babies suffering from at-birth-acquired unilateral or bilateral lesion in the prespeech period of development. On the basis of existing studies and experience in the field, a protocol and methodology for the observation of the phonological development of infants in the period between 6 and 24 months were established. Mothers made notes of the changes in the child's development in a diary specially prepared for the research. The data from the diary and the babies' reaction to the therapy in the logopedic office were inserted into the protocol. The research itself involved an experimental and a control group. The control group consisted of 60 babies without brain lesion, while the experimental group was composed of 30 babies suffering from brain lesion obtained at birth as a result of hemorrhaging, hypoxia, and asphyxia. The phonological development of the babies was observed through the ages of 6, 9, 12, and 24 months. This article demonstrates the significant differences in phonological development between the experimental and the control group. The results of the research show that phonological development in the first 6, 9, 12, and 24 months does indeed exist in the experimental group (despite the differences when compared with the control group) and can be enhanced with early monitoring and logopedic rehabilitation in the case of babies with brain lesion.