SUMMARYDue to the strong distance dependence of tunnelling current on electrode spacing, tunnelling can be used to measure sub‐ångström‐scale displacements. The sensitivity and relative simplicity of this technique make it well suited for applications in highly sensitive accelerometers. We have constructed a cantilever‐type accelerometer in which a mass‐loaded lever deflects freely in response to accelerations. Deflection is measured by tunnelling in the constant current mode between an electrode on the lever and a tunnelling tip positioned by a piezoelectric transducer. Using a lever/mass system with a force constant of 2·3 × 104N/m and an effective mass of 2·4g, we obtained a sensitivity of 79 V/g with a bandwidth greater than 200 Hz. Accelerations smaller than 10−4g could be detected using this device.