Cell-attached and inside-out patch clamp recording was used to compare the functional expression of membrane ion channels in mouse and human embryonic stem cells (ESCs). Both ESCs express mechanosensitive Ca²⁺ permeant cation channels (MscCa) and large conductance (200 pS) Ca²⁺-sensitive K⁺ (BK(Ca²⁺)) channels but with markedly different patch densities. MscCa is expressed at higher density in mESCs compared with hESCs (70 % vs. 3 % of patches), whereas the BK(Ca²⁺) channel is more highly expressed in hESCs compared with mESCs (~50 % vs. 1 % of patches). ESCs of both species express a smaller conductance (25 pS) nonselective cation channel that is activated upon inside-out patch formation but is neither mechanosensitive nor strictly Ca²⁺-dependent. The finding that mouse and human ESCs express different channels that sense membrane tension and intracellular [Ca²⁺] may contribute to their different patterns of growth and differentiation in response to mechanical and chemical cues.