Purpose To describe corneal surface changes in keratoconjunctivitis sicca (KCS). Methods In all 23 patients with KCS were examined with the slit lamp and photographed by non-contact photomicrography. Results Without staining, grey surface cells and small epithelial cysts were visible. Application of fluorescein sodium resulted in two types of micropunctuate (15-30 mum) staining, a nonfluorescent (yellow/brown) and a fluorescent ( green) one, in brilliantly green staining of cysts, and in enlarging fluorescent (green) flecks (70 - 1600 mum) with propensity to confluence. The flecks often developed in inconspicuous areas and showed abnormal subsurface cells. Application of rose bengal resulted in more or less intensively red-stained cells measuring about 30 mum in diameter, often less ( 15 - 20 mum), with or without a centrally located nucleus, individual or gathered in small groups or larger patches, and in confluent staining. Smaller and larger cells, with or without nuclei, weakly or strongly stained, were often located close to each other. The smaller green flecks showed a few centrally located red-stained cells, and the larger ones showed many almost uniform small red-stained nucleated ones. Conclusions Corneal epithelial surface disease in the present KCS patients consisted of unspecific features-such as increased light-reflecting property ( grey cells), disruptions of intercellular junctions ( micropunctuate green fluorescein staining), pathological dye uptake (micropunctuate yellow/brown fluorescein and red rose bengal stainings), and epithelial oedema (microcysts) -and also of features that seemed to be disease specific. Such features were, with fluorescein sodium, focal disruptions of the epithelial barrier function manifesting in enlarging green flecks, and, with rose bengal, abundant nucleated cells, particularly small ones organised in foci. The nature of the abnormal subsurface cells present in the areas of the green flecks, and the mechanisms behind the focal involvement are unclear.