Dry eye syndrome or keratoconjunctivitis sicca (KCS) occurs when there is a deficiency in aquatic fraction of tear--which contains water, lipids and mucus--resulting in dryness, turbidity, corneal pigmentation and hyperemia, conjunctivitis and increased mucus production (1). This may happen in all ages, especially in elderly. Keratoconjunctivitis sicca develops due to several causes such as autoimmunity, hereditary, viral infections, hypothyroidism, hyperadrenocorticism, secondary respond to drugs and surgery (2, 3). A four-year old male terrier was referred to university of Tehran Small Animal Hospital. The disease had developed in the animal since four weeks ago. In this case, a viral infection had been diagnosed within a month, showing respiratory and digestive symptoms. Virus-induce autoimmune mediated KCS was confirmed based on a Schirmer Tear Test (4), persisted symptoms and the case history. Pilocarpin--a muscarinic cholinergic agonist which increases tear secretion by direct affection on autonomic neuron system and hence lacrimal glands--was prescribed (12 h/day/eye drop) followed by oral prescription of the drug.