This report introduces practical techniques and applications of complementary scanning electron microscopy (SEM). To identify the complementary structures at high magnification, we first made a montage pair of low magnification micrographs as a guide map. Consulting the map, we took complementary micrographs at high magnification. When taking a picture at high magnification, we drew the outline of the most prominent structures on a transparent plastic plate attached to the cathode-ray tube of a SEM. Then another picture of the complementary structures was taken after adjusting the complementary structures to the reverse image of the plastic plate. We performed three applications of the complementary SEM: 1) complementary observation of the epithelial underside and lamina propria of the rat urinary bladder; 2) complementary observation of the fractured Golgi apparatus; and 3) evaluation of specimen drying methods. After proper digestion of the rat urinary bladder using strong alkali, the epithelium was detached from the underlying lamina propria. On the basal side of the epithelium, the meshwork of grooves were visible. The observation of the corresponding lamina propria confirmed that the grooves were occupied by blood capillaries located in the uppermost part of the lamina propria. The complementary observation of the Golgi apparatus was useful for understanding its three-dimensional architecture. The observation on both complementary fractured surfaces of the Golgi apparatus from the mouse lacrimal gland demonstrated the continuity of the Golgi stacks. It was also effective for observing both the cis and trans side of the same Golgi stack. Complementary SEM was also useful for evaluating the specimen drying method.(ABSTRACT TRUNCATED AT 250 WORDS)