In this paper we present a keypoint detector based on the bimodality of the histograms of oriented gradients (HOGs). We compute the bimodality of each HOG, and a bimodality image is constructed from the result of this bimodality test. The maxima with highest dynamics of the image obtained are selected as robust keypoints. The bimodality test of HOGs used is also based on dynamics. We compare the results obtained using this method with a set of well-known keypoint detectors.