The number of canine and feline clinical diseases that may be manifested as ocular dysfunction continues to increase. Veterinarians are often presented with sick patients who also have eye disease. Conversely, animals are examined for eye disease that on closer inspection also have a systemic illness. A decision must be made; is there a relationship between the observed ocular and systemic problem, or are they separate morbid processes? If they are related, can the ocular signs be used to better define the systemic illness, chart its course, or establish a prognosis? It is hoped this article will aid the clinician in gaining a better perspective on the complex relationship between the eyes and systemic disease.