The physiologic and anatomic effects of contact lens (CL) wear include both short- and long-term changes in the corneal epithelium stroma, and endothelium. Although these effects can arise in all lens wearers, they are of greatest concern in users of extended wear lenses, owing to their association with an increased incidence of sight-threatening complications. The complications attendant on extended wear may be patient related, lens related, or care related, but they are not inevitable. Patient-related complications can be minimized if clinicians pay close attention to patient selection, lens fitting, and follow-up. Complications related to lens wear and care can be minimized if patients (a) follow the proper lens wear regimen; (b) observe appropriate lens care routines; (c) follow the proper lens disposal regimen; (d) monitor the appearance, visual acuity, and well-being of their eyes; and (e) immediately report any irregularities or changes in ocular status to their doctor. To ensure that such rules are observed, practitioners must educate their patients as well as their staff in these matters. They must also instruct patients not to wear extended wear lenses longer than 7 days at a time and to allow for an overnight respite from lens wear after this period of use.