In three lexical decision experiments and one progressive demasking experiment, performance on low-frequency heterographic homophones having a high-frequency mate was compared with performance on non-homophone target words with or without high-frequency orthographic neighbours. Robust homophone interference effects were observed in all experiments, as well as inhibitory effects of neighbourhood frequency. When speed-accuracy trade-offs were reduced, the homophone interference effects were found to be additive with effects of high-frequency orthographic neighbours. Furthermore, the size of homophone interference effects increased when pseudohomophone stimuli were presented among the nonwords. These results are tentatively interpreted within the framework of a bi-modal interactive activation model.