Blepharoptosis is the downward displacement of the upper eyelid secondary to structural abnormalities (muscle or aponeurosis) or neurologic problems. It is a frequent condition and its clinical picture varies from a cosmetic discomfort to severe visual dysfunction, depending on the pathogenesis and the degree of ptosis. The diagnosis of ptosis is complex and goes beyond simple clinical examination. Ptosis surgery is perhaps the most challenging in the field of oculoplastics, especially in congenital cases and neuromuscular disorders. This paper discusses some concepts in blepharoptosis with emphasis on diagnosis and surgical principles.