Our laboratory's recent work on the nature of masking has revealed that stimulus change can cause both forward and backward maskinglike effects. In these previous demonstrations, a decrease or shift in the noise contained in the signal channel constituted the stimulus change. To demonstrate that these masking effects were attributable to stimulus change and not the interaction of off‐frequency transients, we designed the present experiment in which the stimulus change occurred in the nonsignal ear. In this case, stimulus change consisted of a shift in correlation of the noise between the two ears by inverting the contralateral noise at various times (4<Δt<200 msec) prior to the onset of the potential signal. Relative to the unchanging (+1 or −1) contralateral noise control conditions, the detectability of the signal was significantly decreased independent of the direction of change in correlation (+1 to −1, or −1 to +1). Effects of differing rise‐fall times (1, 2.5, and 5 msec) of noise change were also examined. The results are discussed in terms of current masking theory. [This research was supported by a grant from NINDS.]