Numerical experiments are performed to investigate the effects of the bottom slope of a western boundary on realistic warm-core rings, using a primitive equation sigma coordinate model. Warm-core rings which initially have baroclinic velocity near a steep bottom slope gradually move northward, but those with barotropic velocity do not. Barotropic velocity on the slope immediately disperses as a topographic Rossby wave, while baroclinic velocity is retained. Since the northward movement is caused by an effect very much like the image effect which is originally the effect of a free-slip wall, the authors term this effect the equivalent image effect. The equivalent image effect increases as a slope becomes steeper and bottom friction becomes weaker, and vice versa. It seems that a steep slope acts like a wall, and the bottom friction of a steep slope corresponds to the lateral viscous effect of a wall. However, the effect of a slope on a warm-core ring is different from that of a wall in that ring-slope interactions take place at the lower part of the ring. Because the velocity of a warm-core ring is weak in deep layers, ring-slope interactions are moderate and the leakage of the interior fluid of a ring seen in ring-wall interactions is not apparent, while the viscous effect is weaker than that of a no-slip wall as well. These results are applied to the northward movement of Kuroshio warm-core rings and to warm eddies in the Gulf of Mexico. ¿ 2001 American Geophysical Union