This study was performed as one phase of an extensive research program focusing on the seismic behaviour of precast connections carried out in Middle East Technical University. The primary objective of the research program was to observe and investigate the seismic behaviour of the connection detail proposed by the collaborating company and the specimens with improved details, in order to develop a 11 moment resisting precast concrete beam-to-beam connection". In this study, six beam-beam connection subassemblies were tested under reversed cyclic loading simulating severe earthquake action. The first specimen was a monolithic specimen used as a reference specimen and tested to define the reference behaviour. The second specimen was a precast specimen, which was detailed by a company specializing in precast concrete production. The remaining specimens were modified according to the results of the formerly tested specimens. All of the specimens were identical in dimensions. All test specimens were 1/2.5 scaled models of the improved connection details used in the highly critical earthquake zones. The behaviour of the precast members was compared with that of the reference one and with the others. In order to improve the seismic performance of the connection, several recommendations for future research and practices are also given in the context of the paper. (c) 2005 Elsevier Ltd. All rights reserved.