Both temporal and spectral masking have been studied extensively in the literature. Mostly, they have been regarded as separate phenomena. Very little is known about the interaction between these two effects, i.e. masking in the time‐frequency domain. Data on the time‐frequency spread of masking evoked by a single Gaussian‐shaped tone pulse are presented in an accompanying study at the same conference (Necciari et al.). The current study gathers data on the additivity of masking by up to four, approximately equally effective Gaussian maskers (ERB=600 Hz), separated either along the time or the frequency axis. For temporal separation, the amount of masking increases with the number of maskers, with excess masking (exceeding linear additivity) of up to 25 dB. For frequency separation (preliminary data) excess masking amounts up to 15 dB, and the higher‐frequency masker (relative to the target) contributes more to the additivity than the lower‐frequency maskers. Experiments with multiple maskers combining both temporal and frequency separation are underway. Combined with the single maker data, these data may serve as a basis for modeling time‐frequency masking effects in complex signals. Work partly supported by OEAD (WTZ project AMADEUS) and ANR