In the present study, the effects of long-term hypoxia on cultured glomus cells of rat carotid body were investigated. Spraque-Dawley (SD) rats (weighing about 100 g) were kept in a decompression chamber for 7-10 days to simulate the environment at an altitude of 5,000 m above sea level at first. Then the carotid bodies were removed from the anesthetized animals and dissociated to obtain individuals or small clusters of glomus cells. These cells were cultured under hypoxic condition (11% O2, 5% CO2, 84% N2) for 2-3 days. Control samples from normal SD rats (normoxic rat) were cultured in normoxic (21% O2, 5% CO2, 74% N2) or hypoxic conditions. Intracellular pH (pHi) and membrane potential (MP) of glomus cells of both the groups were simultaneously measured with pH-sensitive and conventional microelectrodes. The results indicate that: (1) Long-term hypoxia decreased pHi and increased MP of the cultured glomus cells to a degree far greater than acute hypoxia did; (2) The mean pHi and MP of the glomus cells of the normoxic rat, but cultured under hypoxic environment, recovered approximately to control values when measured under normoxic condition, whereas those of the long-term hypoxic rat cells did not.