Sodium hyaluronate solutions have been advocated in the management of a variety of dry-eye states. By virtue of their non-Newtonian rheological properties, formulations exhibiting high zero-shear viscosities may be used as an artificial tear with the expectation of prolonged precorneal residence times and improved tolerance. Quantitative gamma scintigraphy was used to evaluate the residence times of 0.2% and 0.3% sodium hyaluronate solutions and a polymer-free solution of buffered saline in 12 patients with keratoconjunctivitis sicca and a group of six normal volunteers. Using several indices of residence time, mean values for the sodium hyaluronate solutions were significantly longer than those for buffered saline. Parallel changes in tear film thickness were also demonstrated using a technique based on laser interferometry.