Recent results have shown that the osteoblast like MG-63 cells were good polarised with a resting membrane potential of about –60 mV. Moreover it was found that injection of depolarising currents could induce repetitive action potentials in the cells. Electrophysiological and molecular biological analysis showed that the polarisation and the action potentials were related to functional expression of the strong rectifiers K_ir2.1, 2.3, and 2.4 channels, the tetrodotoxin (TTX) sensitive Na_v1.3, 1.4, 1.6, and 1.7 channel subtypes as well as the slow activated K_v2.1 channel. Additionally we show here for the first time that MG-63 cells express functional acethycholine receptors. The results indicate that the osteocarcinoma MG-63 cells are excitable. To analyse whether this excitability of the GM-63 cells is common to other osteoblast like cells, the Sa-Os, U2-Os, and the mesenchymal stem cells Heca-BVB were studied. Strong K_ir channels related currents were found in Heca-BVB. Reduced K_v currents were observed in all three cell types, while Na_v related currents were not found in either cell type. The role of the excitability in osteogenesis and malignant development is discussed.