When a speech signal is obscured by a second simultaneous competing speech signal, two types of masking contribute to overall performance. Traditional "energetic" masking occurs when both utterances contain energy in the same critical bands at the same time and portions of one or both of the speech signals are rendered inaudible at the periphery. Higher-level "informational masking" occurs when the signal and masker are both audible but the listener is unable to disentangle the elements of the target signal from a similar-sounding distracter. Because "informational masking" is restricted to cases where the masking signal is similar to the target signal, it has a much greater impact on performance when a speech signal is masked by speech than it does when a speech signal is masked by noise. Furthermore, its effects depend specifically on the characteristics of the target and masking speech signals. This brief chapter outlines the results of some recent experiments we have conducted in our laboratory that have examined the role that informational masking plays in speech perception and attempted to isolate the effects that informational and/or energetic masking have on multitalker listening.