A set of experiments which assesses the ability of human observers to monitor two earphone channels for the purpose of performing one or two independent and simultaneous frequency difference‐limen tasks is described. Performance (d′) was significantly poorer with dichotic stimulus presentation than with monaural, control conditions. Under dichotic presentation conditions, performance was equivalent whether the observers were instructed to listen to one or both channels. A detailed analysis of the data indicated that the observers could discriminate a change but seemed to have difficulty in identifying the channel in which the change occurred. Consistent with results reported in the simultaneous signal‐detection literature using intensity detection or discriminations, we found that observers cannot successfully monitor more than one channel. It is suggested that when the dichotic stimulus presentation provides useful information which is not present during monaural tasks (i.e., lateralization cues), observers may be able, using this added information, to perform a divided attention task with little or no apparent performance decrement relative to single‐channel tasks.