The emission lines in the quiescent spectrum of the recurrent nova T Coronae Borealis are variable. Optical spectra recorded during the years 1985-90 show one full cycle of high and low states. After removing the slow variation, an orbital-phase-dependent variation becomes apparent in the H-alpha line, with maxima around orbital phases 0 and 0.5. The slow variation indicates secular changes in the accretion disk possibly caused by a variable mass-transfer rate. Orbital variations can be caused either by geometrical effects or a phase-modulated mass-transfer rate. More detailed monitoring is needed to model the system.