This light and electron microscopic study demonstrates an elastic fiber network (EFN) for the levator palpebrae superioris muscle complex, which forms an intricate insertion into the upper eyelid. The EFN is examined in the monkey, in a fresh exenteration specimen, and in fresh frozen cadaver specimens from both sexes of different age groups. Multiple elastic insertions of the levator aponeurosis and Muller's muscle attachment with well-organized elastic fibers are demonstrated using special staining techniques and serial microscopic sectioning. Transmission electron microscopy (TEM) confirms the ultrastructure of "mature" elastin fibers in Muller's muscle tendon and their close relationship with the elastin-related fiber, oxytalan. Current thinking concerning the nature of elastic fibers and their possible implications in acquired involutional blepharoptosis is discussed. This microscopic study of the EFN of the upper eyelid focuses attention on the multiple elastic fiber insertions of the levator muscle complex that includes the levator aponeurosis, the conjoined fascia, the lid crease area, and Muller's muscle tendon, which have not been previously described.