Parasitic infestation is a major health problem in tropical countries. Increasing tourism and the influx of refugees from Southeast Asia demand a greater awareness of ocular parasitology. In Thailand, cysticercosis, gnathostomiasis, and angiostrongyliasis are the three commonest ocular parasitic diseases. No antiparasitic drugs are yet available to treat ocular involvement, and therapeutic success depends upon early and complete surgical removal. Because the eye is the only site at which direct visualization and surgical removal are possible, ocular examination is crucial to diagnosis and treatment.