A fundamental limiting factor in the precision of magnetostratigraphic correlation is stratigraphic completeness. Sadler (1981) has suggested a method by which the expected completeness of any given stratigraphic section can be calculated given the thickness, duration, and depositional environment. The technique is probabilistic and requires the investigator to specify a meaningful short-term time scale at which completeness is to be estimated. For magnetostratigraphy, the short-term time scale is defined by the duration of the polarity chron or other polarity feature of interest. Sadler's method allows the probability of observing such features to be quantified. It is a useful tool for evaluating the reliability of magnetostratigraphic correlations and for judging between alternative correlations.