The large number of potentially retinotoxic drugs and their effects at multiple structural sites, from pigment epithelium to retina and optic nerve, imply complex diagnostic procedures rather than a single test. Early diagnosis of retinotoxicity, however, can be established by through history, ophthalmoscopy and routine (simple) functional tests carried out by the responsible ophthalmologist. In case of suspected damage of the retina or of the optic nerve electrophysiology, angiography, selective perimetry and color vision tests are recommended. In this outline chloroquine retinopathy is discussed in detail.