Silica gels with both macropores and mesopores were prepared from water glass by fixing transitional structure of phase separation, and their strength was investigated. Pore structure of the gels was controlled by changing gel-preparation compositions, aging conditions and calcination temperature. Strength of the gels varies depending on the mesopore volume. At the same time, porosity of the gels decreases with decreasing mesopore volume, and correlation between strength and porosity is recognized like other porous systems. The strength of the bimodal porous silica gel is somewhat larger than that in literature for the silica aerogel with similar porosity. (c) 2005 Elsevier Ltd. All rights reserved.