Abstract: A highly sensitive microbend horizontal fiber-optic accelerometer has been conceived, particularly useful in seismological research where minute accelerations must be detected. The device uses a cantilever beam and the compliance of an optical fiber mounted between deforming teeth to act as the springs in the accelerometer's spring-mass system. Acceleration is detected by sensing the changes in the intensity of light propagating through the deformed fiber due to the motion of the mass relative to the case. Accelerations as small as 5 .mu.g at 1 Hz can be detected with a dynamic range of 100 dB.