The solidification structure of Ag-Cu eutectic alloy at different undercoolings was investigated. A critical undercooling of 76 K is revealed, at which a transition from cellular to dendritic growth of lamellar eutectic occurs, accompanied with an abrupt rise of growth velocity. It is suggested that the large difference in composition between the two eutectic phases and the very large thermal diffusion coefficient of the liquid result in the cellular growth of lamellar eutectic at low undercoolings. (C) 2008 Elsevier B.V. All rights reserved.