We propose to use the combinatorial assignment problem to model the issue of associating ground-truth and declared edge pixels in the objective empirical performance evaluation of edge detectors. The assignment problem is adapted to the maximal assignment problem to incorporate the need for tolerating certain amount of localization error for the detected ground-truth pixels. The solution to this problem yields a maximal one-to-one association between ground-truth and declared edge pixels. Performance evaluation based on this association has the attitude of making the most positive interpretation of the declared edge map. Synthetic test data is used in the experiment to allow unambiguous subjective judgment of edge detection performance. The preciseness and reasonableness of the performance evaluation from the proposed method is observed. The usefulness of this method in other performance evaluation applications is also discussed.