The eutectic composite to primary deudritic transition in Al-Cu alloys near eutectic composition has been studied at various solidification conditions. Structures produced upon solidification of the eutectic composition (33.0wt% Cu) of Al-Cu alloy have been studied as a function of solidification rate. The results obtained from this study were as follows; 1. As solidifiation rate increased, the range of eutectic composite zone had been extended to aluminum-rich compositions. 2. At the rapid solidification rates, primary Al was formed at rod-shaped colonies, whereas primary CuAl₂formed at fine lamellar composite zone. The primary CuAl₂was aligned parallel to the direction of heat flow. 3. The lamellar composite of Al-CuAl₂eutectic was arranged in the form of rod-shaped colonies at rapid solidification rates. The colonies were aligned parallel to the direction of heat flow, whereas the lamellar within the colonies aligned at various angles, as high as 90 deg. to the direction of heat flow. 4. A duplex dendritic structure was produced at slow solidification rates. 5. The colony spacing, lamellar spacing and the ratio of colony spacing to lamellar spacing increased with a decrease in the solidification rats.