Abstract: The present invention provides a tilting control assembly for a chair which comprises a support mechanism mounted on a chair leg post, a chair seat carried by the support mechanism, and a chair back arranged behind the seat. At least one of the seat and the back constitutes a tiltable member. The tilting control assembly comprises at least one tilting control spring for elastically supporting the tiltable member via at least one contact member, and an adjusting mechanism which is automatically responsive to the weight applied to the seat for causing relative displacement between the tilting control spring and the contact member in a manner such that the spring constant of the tilting control spring increases as the applied weight increases.