Sodium hyaluronate eyedrops can relieve various dry eye symptoms by prolonging the stability of the precorneal tear film. To determine the most effective concentration of sodium hyaluronate, we studied the concentration-dependent effects of sodium hyaluronate eyedrops on the precorneal tear film breakup time (BUT) in 12 volunteers. These subjects had a BUT of 10 seconds or less and a low tear volume determined with the phenol red thread test. They received four different concentrations of sodium hyaluronate eyedrops (0, 0.05, 0.1 and 0.3%). BUT was measured noninvasively using a non-contact specular microscope before the sodium hyaluronate eyedrop instillation and again after 5, 15, 30, 60, 120 and 180 minutes. The tear film stability period was prolonged significantly with 0.1% and 0.3% eyedrops at all measurement times (P < 0.05), while the eyes treated with 0% and 0.05% eyedrops showed no significant prolongation of tear film stability at any measurement times. The findings of this study confirm that sodium hyaluronate at a concentration of at least 0.1% is required to delay the breakup of the precorneal tear film.