The ocular surface is dependent on the physiological and anatomical integrity of the eyelids and associated adnexal structures. Entropion and ectropion are commonly encountered in clinical practice, and pose a risk to the success of both ocular surface and intraocular surgery. This chapter covers the causes of such lid malpositions, which can be congenital or acquired (e.g. involutional, cicatricial or paralytic) and the clinical examination of the eyelids. Principles underlying corrective surgery are demonstrated and practical aspects of the some more commonly performed and effective operations are described.