A toy construction system is provided for permitting the construction of a variety of different structures in varying sizes and shapes. The toy construction system includes a plurality of elongated rod members and a plurality of substantially flat connector members which may be interconnected in different combinations. Ball elements are provided on certain of the members which are adapted to engage complimentary socket elements contained on other members in order to rotatably interconnect the two members. The socket elements include means for positively retaining the ball elements within the socket elements and means for facilitating the insertion and removal of the ball elements into and out of said socket elements. The members may further include coupling element for rotatably engaging other members including spherical means. The members may still further include means for engaging other members by the use of a releasable hinge. A power transmission unit may be further included.