Dissociated cells of cerebral hemispheres from 8-day-old chick embryos were cultivated for 8 days in polylysine-coated Petri dishes. Changes of DNA, RNA, total proteins, putrescine, spermidine, spermine, free amino acids and enzymes involved in polyamine and GABA metabolism were studied throughout neuronal development in culture. The presence of GABAergic neurons in the cultured cell population was demonstrated. There were time-dependent changes in cellular polyamine concentrations and the activities of the enzymes involved in polyamine metabolism. Since no significant proliferation took place after the first day in culture, the observed changes indicate a role of polyamine metabolism during neuronal differentiation; it was not possible, however, to attribute the observed changes to specific functions. This culture system seems especially useful for the study of biochemical and of functional correlations between GABA and polyamine metabolism and morphological and functional developments of neurons.