This study focused on how formwork surfaces affected concrete lateral pressure when surface drainage was provided and their surfaces were covered with liners. Seven forms were constructed using different surface materials. On the surfaces of three forms, drainage was provided and different types of geotextile liners were used. The other forms were used as references. For comparison, the lateral pressure of concrete was calculated by ACI 347. Concrete was placed into the forms and the lateral force of concrete on the form surface was measured by a strain gauge measurement system. It was Concluded that the concrete lateral pressure could be decreased by some 40%, using a drainer system on the formwork surface and covering the surface with liner. (C) 2002 Elsevier Science Ltd. All rights reserved.