Expressions approximating the probability of error for digital magnetic recording systems utilizing peak detection are examined. The effects of zero-crossing shift and spurious zero-crossing creation in the signal at the input to the zero-crossing detector are included. These error rate expressions are used to evaluate the performance of a typical fixed head recording system for various equalization schemes. Optimum equalizer parameters arise due to trade-offs between the amount of pulse-slimming and the signal-to-noise ratio degradation given by the equalizer. Additional error sources associated with rotary head recording systems operating at high data rates are briefly discussed.