Aggregate structures of steroids adsorbed on electrically-poled hydroxyapatite (HAp) ceramics were investigated by X-ray diffractometry (XRD) and scanning electron microscopy. Effectivity of the poled HAp on modification of the steroid assembly modes was discussed by the arrangement estimations of the steroid molecules. The dense HAp ceramics were obtained from the pelletized HAp powder precipitated from calcium hydroxide suspension and phosphoric acid using conventional sintering at 1250°C under the saturated water vapor pressure. The HAp ceramic blocks were poled in a DC electrical field of 1.0 kVcm-1 with being heated at 300°C. The HAp ceramics were immersed in ethanol solution of steroids at 37°C. The steroid crystals were overgrown onto the HAp substrates by recrystallization method. In the case of cholesterol, the tabular crystals of cholesterol monohydrate and the needle-like crystals of anhydrate were overgrown on all of the HAp ceramic surfaces. The thickness of the cholesterol layers on the positively (p) poled HAp surfaces was considerably less than those of the negatively (n) poled and non-poled (0) surfaces. The remanent chaige of the HAp ceramics altered the morphology of vitamin D3 crystals deposited on the HAp surfaces. It was revealed that the electrically-poled HAp ceramic surfaces changed the aggregate structures and the crystal growth rates of steroids.