Development of the sympathetic neurons of the dissociated cranial cervical ganglia taken from newborn rats has been studied in tissue culture. Vital microscopical, histological, histochemical and electrophysiological methods have been used, as well as an automatic morpho- and cytospectrometrical computer analysis. Active processes of the neurocyte regeneration and development begin on the 3d-4th day of cultivation. Average areas of the cellular body optic cross section increase more than two times, and an average size of nuclei-1.8 times. Some processes appear. An active synthesis of catecholamines takes place, its location coinciding with the forming chromatophilic substance zones. The end of the first and the beginning of the second week of cultivation is characterized with an active growth of processes, with formation of a complex neuropil, with differentiation of the neurite terminal parts. Catecholamines are displaced towards the processes. A spike activity to the intracellular electric stimulation appears. The first intraneuronal contacts are established. At the end of the second and during the third week the cells reach their maximal size. The ratio of the cytoplasm cross section area to the nuclear cross section reaches its constant level. The catecholamines concentration in the neuronal soma corresponds to its maximal values. Chromatophilic substance and the neurofibrillar apparatus are formed. On the neuronal soma pericellulars are formed. There are not any essential changes after the third week of incubation.