A Monte Carlo technique is used to predict the influence that magnetic dipolar interations have on thermodynamic ordering in dispersions of fine magnetic particles. The interactions give rise to Curie–Weiss‐like behavior with an ordering temperature that is found to vary linearly with particle concentration. The dependence of the ordering temperature on packing fraction is in agreement with predictions from analytical treatments. These observations have important implications in the characterization of magnetic liquids. In particular it confirms that many of the techniques used to calculate particle size distribution parameters will give misleading results unless the measurements are made on very dilute systems.