The melting point of ice in trehalose and sucrose solutions was measured by in situ observations of a minute ice crystal. It was found that the concentration dependence of the melting point of ice in both trehalose and sucrose solutions was identical. Such a concentration dependence of the melting point was in agreement with the equation of freezing point depression for dilute aqueous solutions up to about I molal. In addition, the measured values of the melting point decreased rapidly with an increase in the concentration. These experimental results for an equilibrium state were discussed by comparing them with the results for a nonequilibrium state, i.e., the results obtained for growing ice crystals in saccharide solutions. (c) 2006 Elsevier B.V. All rights reserved.