A cell-automaton model for a binary eutectic system has been developed. This study examines a Bridgeman-type temperature field with periodic boundary conditions. A stable operating range of lamellar spacings is obtained based on the parameters of the temperature field. The undercooling of the liquid phase ahead of the solid/liquid interface is also estimated in the calculations. The estimated lamellar spacings and undercoolings agree well with the predictions of the Jackson-Hunt model. (doi:10.2320/matertrans.M2009304) Eutectic alloys are used widely in industrial materials such as cast iron (Fe-C), silmin (Al-Si) and soldering alloys. In addition to this use, the benefit of eutectic materials as in-situ composites has attracted attentions. Namely, the minor phase acts as a physical function and the major phase supports the full strength of the material, compensating for the lack of strength of the minor part. Therefore, in order to develop a new functional structure as a composite material, control of the eutectic solidification would be a key technique. Generally speaking, the methods of studying the formation of the structure of alloys can be divided in three ways. The first is the observation of structures and the measurement of specific parameters by experiment. This might be considered the starting point for all the scientific research. Secondly, the researchers try to construct analytical models which can predict the phenomena observed in the experiments. Using basic physical equations and presuming that a few effects of the thermodynamic ''force'' control the phenomena and that other effects can be regarded as negligible, a series of equations can be developed with suitable boundary/initial conditions. The solutions of the equations are obtained by an analytical method (or numerical calculations). The predic- tions of the analytical method, in turn, should be examined by experiments. As for the third method of study, numerical simulations have recently been developed. These include Monte Carlo simulations, phase-field methods, cell-autom- aton methods, etc. In numerical simulations, basic calculation rules are also formulated, but the effects of the rules are not considered prior to calculation. The effects are recognized after the calculations are performed. In the field of study concerning eutectic growth, analytical models were explored after World War II. 1-4) In these studies, the Jackson and Hunt (JH) model 4) presented not only analytical solutions for the specific spacing and undercooling of the lamellar and rod-like regular eutectic growth, but also a hypothesis for the adjustment of the specific spacing. Irregular eutectic growth models have also been proposed. 5,6) The JH model has also been extended to rapid solidification condition. 7) The methods of the JH model have also been applied to the growth of the three-phase structure with regular lamellar, rod + hexagon and semi-regular brick-type mor- phologies. 8) In 1994, J. A. Spittle and S. G. R. Brown studied a 3-D cellular automaton model of coupled growth in two- component systems. 9) They obtained lamellar structures in undercooled two component melts using a simple algorithm. In this work, we wish to compare the results of a 2-D cell-automaton model with those of the JH model. By introducing temperature fields moving with constant veloc- ities (Bridgeman-type temperature fields) into the cell- automaton program, it can be determined whether quasi- stationary solidifications are obtained, and therefore the results of the cell-automaton program can be compared directly with the prediction of the JH model. The lamellar spacing and the undercooling of the liquid at the solid/liquid interface will also be examined. 2. Algorithm and Parameters of Calculation for the 2-D Cell-Automaton Model