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Tear levels of certain cytokines/chemokines can potentially serve as biomarkers for dry eye and other ocular surface diseases if they remain stable from day-to-day in healthy eyes. The aim of this study was to determine the normal intra- and inter-day variation of selected tear cytokines/chemokines. Tear samples from 24 young, healthy adults were collected 11:00 AM–1:00 PM (mid-day) and 5:00–7:00 PM (evening) on three non-consecutive days. Concentrations of 18 cytokines/chemokines (EGF, eotaxin, CX3CL1/fractalkine, GM-CSF, IFN-γ, IL-10, IL-1β, IL-13, IL-17A, IL-1RA, IL-5, IL-6, CXCL8/IL-8, IL-9, CXCL10/IP-10, CCL5/RANTES, TNF-α, and VEGF) were measured by multiplex bead analysis. Ocular surface disease was ruled out by clinical tests. A random-effects ANOVA model was used to evaluate intra- and inter-day effects on cytokine/chemokine levels. Repeatability of intra-subject inter-day measurements …