Immediate memory for verbal material and complex patterns was monitored in neurosurgical patients during electrical stimulation via electrodes implanted in the left and right cingulum or hippocampus. A severe memory disorder for verbal memoranda accompanied left, but not right, cingulum stimulation. The converse was true when nonverbal recognition was evaluated, stimulation of the right but not the left cingulum being associated with a deficit in recognition of random patterns. Comparable stimulation in the region of the left and right hippocampus failed to interfere with patient performance on the identical memory tests. A separate group of patients who had undergone unilateral temporal lobectomy was also evaluated and showed a normal memory span for verbal and nonverbal information. These groups, however, were unable to store or to retain information which exceeded their memory span. The findings support the notion of a dual mechanism for memory, implicating specific limbic structures that regulate ''affective coding'' and ''storage''.