A new qualitative test for the study of conjunctival mucus has been developed. Conjunctival scrapings were obtained from 196 patients. Microscopic mucus ferning (arborization) was observed in 148 (91%) patients with various forms of acute conjunctivitis. Six patients (18%) with cicatrizing conjunctivitis (diffuse conjunctival cicatrization, ocular pemphigoid, Stevens-Johnson syndrome) had mucus ferning in their conjunctival scrapings specimens. Mucus ferning was significantly absent (P less than 0.005) in patients with diffuse conjunctival cicatrization when compared to mucus ferning in other forms of conjunctivitis. Ocular mucus ferning test is a simple inexpensive office test for the evaluation of patients with mucus deficiency.