Using a two-alternative temporal, forced-choice technique (2ATFC), the detectability of a 250 Hz, 128 msec tonal signal masked by a gated tone of the same frequency and duration was measured as a function of the signal level, the phase angle at which the signal was added to the masker, the masker level, and the interaural phase difference of the signal. When the interaural phase difference is 0° and the signal-masker phase is varied, the detectability of the signal is found to follow a simple energy- or power-detection model. At the two signal-masker phase angles used (0° and 90°), the signal-to-masker level required for 75% correct detection in the 2ATFC task remained constant when the masker level was varied. When the interaural phase difference is 180°, the lateralizability of the signal is found to be independent of the signal-masker phase angle. At signal-masker phase angles of 0° and 90°, the signal-to-masker level required for 75% correct detection in the 2ATFC task remained constant when the masker level was varied. The results are discussed in terms of the Durlach equalization-cancellation model of binaural masking-level differences and in terms of the Weber fraction. [The research was supported in part by a PHS Pre-Doctoral Fellowship.]