“Backward masking” is the term used to denote the situation in which one auditory stimulus is masked by another auditory stimulus which follows it in time while in “forward masking” the temporal positions of masking and masked signals are reversed. In this study, backward and forward masking were investigated for both monotic and dichotic conditions using white noise as the masking signal and a 1000‐cps probe signal. Results indicate that monotic backward masking occurs over intervals up to 50 msec while, for the dichotic condition, backward masking occurs for intervals as long as 15 msec. Less monotic forward masking is obtained for brief masking intervals and very little dichotic forward masking is observed. These findings are considered in relationship to other experimental results.