In a group of patients with keratoconjunctivitis sicca associated with Sjögren's syndrome, the Schirmer values were lower in the Sjögren group of patients in comparison with a comparable group in which KCS was not associated with any systemic disease and these differences reached almost statistical significance. But a significant decrease in tear fluid lactoferrin concentration and tear film break-up time was demonstrated. The combination of the tear fluid lactoferrin concentration, the Schirmer I test values and the tear film break-up time provides a basis for differential diagnosis that is of some value clinically. None of these parameters in itself appeared to be of any clinical value to differentiate between KCS patients who were or were not associated with Sjögren' syndrome.