Calcium phosphate bioceramics, especially those in hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), are leading candidates for scaffolds used in regenerative medicine for bone tissue. The precise control of chemical composition, pore structure, and crystal faces is important for both the tissue regeneration and bioresorption of the materials. The excellent characteristics of HA and β-TCP for cell activity could be shown by using transparent ceramics of HA and β-TCP. Both calcium phosphates prepared through hydrothermal processing composed of rod-shaped particles were compared to conventional materials prepared by sintering methods, and their superior properties for bone regeneration were demonstrated. The in vivo behavior of HA and β-TCP is discussed from the viewpoint of chemical dissolubility.