K⁺ -selective ion channels were studied in excised inside-out membrane patches from human osteoblast-like cells(G292). There classes of K⁺ channels were present and could be distinguished on the basis of conductance. Conductances were 270±27 pS, 113±12 pS, 48±8 pS according to their approximate conductances in symmetrical 140 mM KCI saline at holding potential of -80 mV. It was found that the small conductance (48 pS) K⁺ channel activation was dependent on membrane voltage. In current-voltage relationship, small conductance K⁺ channel showed outward rectification, and it was activated by the positive potential inside the membrane. In recordings, single channel currents were activayed by a negative pressure outside the membrane. The membrane pressure increased P_open of the K⁺ channel in a pressure-dependent manner. In the excised-patch clamp recordings, G292 osteoblast-like cells have been shown to contain three types of K⁺ channels. Only the small conductance (48 pS) K⁺ channel is sensitive to the membrane stretch. These findings suggest that a hyperpolarzing current, mediated in part by this channel, may be associated with early events during the mechanical loading of the osteoblast. In G292 osteoblast-like cells, K⁺ channel is sensitive to membrane tension, and may represent a unique adaptation of the bone cell membrane to mechanical stress.