We have investigated whether the differentiation potential of attached cultures derived from the mouse lateral ganglionic eminence (LGE) is influenced by in vitro expansion. Primary neuronal cultures derived from the LGE give rise to neurons expressing the striatal projection neuron markers Islet1 (ISL1) and dopamine and cAMP-regulated phosphoprotein of 32 kilodaltons (DARPP-32) as well as the olfactory bulb interneuron marker Er81. Our previous results showed that after expansion in vitro, LGE precursor cells can be induced to differentiate into neurons which exhibit molecular characteristics of the LGE, such as the homeobox transcription factors DLX and MEIS2. We show here that while attached LGE cultures maintain Er81 expression through five passages, they lose the ability to generate ISL1- or dopamine and cAMP-regulated phosphoprotein of 32 kilodaltons-expressing neurons already after the first passage. This indicates that the expansion of LGE precursor cells restricts their differentiation potential in vitro. Interestingly, the undifferentiated LGE cultures retain the expression of both the Isl1 and Er81 genes, suggesting that precursor cells for both striatal projection neurons and olfactory bulb interneurons are present in these cultures. Thus the restriction in differentiation potential of the expanded LGE cultures likely reflects deficiencies in the differentiation conditions used.