An adaptive data slicer which functions to adapt to changes in the properties of a signal input thereto by producing a near optimal slicing threshold in accordance with the input signal for use in a decision circuit. The slicing level is considered optimal when its use in the decision circuit minimizes the bit error probability. The data slicer utilizes two peak detectors, a maximum peak detector for detecting the highest levels of the input signal and a minimum peak detector for detecting the lowest levels of the input signal.