Abstract: A sofa bed mechanism for use on a foldable bed frame having a head section, an intermediate section, and a foot section, comprises a rear linkage assembly on a support member operable to control movement of the bed frame in between extended and folded sofa positions, a pivotal leg extending from each of the foot and intermediate sections, a front linkage assembly connected to the legs and to the rear linkage assembly for moving the legs into downwardly extending support positions in response to movement of the bed frame to the horizontal position and means extending between the front and rear linkages which maintains downwardly directed forces on the legs to prevent the folding of the bed frame from the horizontal position toward the folded sofa position in response to a downwardly directed load on the head section.