We show the possibility of unidirectional freezing of colloidal random suspensions as a novel method for growing colloidal crystals. First we confirmed the rejection of polystyrene particles from unidirectionally growing ice water interfaces by observing color gradations of colloidal crystals formed in front of the interfaces. The rejection of particles from the growing interfaces increased particle concentration in the colloidal crystals. Then we succeeded in achieving colloidal crystallization in front of ice water interfaces during the unidirectional freezing of water suspensions of polystyrene particles. The colloidal crystals thus brained exhibited a columnar shape that is typically observed in the unidirectional colloidal crysrallizarion using centrifugation. (C) 2013 Elsevier B.V. All rights reserved.