A novel infant child restraint system that includes a base having a height adjustment to allow the base to assume one of a plurality of positions and inclinations when mounted to the vehicle seat. Additionally, in certain embodiments the base is formed to have a recessed knee-receiving area, into which the user can place their knee when tightening the vehicle's restraint system around the base. The base and car seat are removably attached in interlocking relation using a novel connection mechanism that is not susceptible to premature or improper release due to forces, regardless of the direction of such forces. This mechanism is independent of the car seat handle. Furthermore, this connection mechanism includes a simple manual disconnect or release system, to allow quick removal of the seat from the base.