Objective To report four subjects with a combination of floppy eyelid syndrome, mental retardation, and increased mechanical stimulus to the affected side. Design Retrospective, noncomparative case series. Participants The authors retrospectively reviewed the charts of four mentally retarded subjects with floppy eyelid syndrome. Intervention Surgical tightening of three upper lids and one lower lid was performed in three subjects. Main outcome measure Relief of symptoms. Results The affected eyelids were treated surgically; in case 1 by anterior lamellar repositioning and lateral and medial canthal tightening, in case 2 by horizontal upper lid shortening, and in case 3 by horizontal lid shortening of both upper and lower lids. There was marked relief from symptoms in all three cases. In case 4, surgery was deferred at parental request. Conclusions These cases support the role of mechanical factors in the pathogenesis of floppy eyelid syndrome. Subjects with mental retardation may cooperate poorly with examination, and we believe that there should be a careful search for floppy eyelid syndrome in the presence of chronic conjunctivitis or unexplained epitheliopathy.