Four prolonged episodes of partial complex status epilepticus were observed in a teenaged girl. During each there was an "ictal" phase, in which her mental state frequently fluctuated between mildly clouded consciousness and almost total unresponsiveness; once, she was also blind during this phase of impaired consciousness. With therapy, the periods of unresponsiveness became less frequent and less prolonged until a second, "postictal," phase occurred when she was alert, but with profound retrograde and anterograde amnesia that gradually resolved in several weeks. The "ictal" EEG pattern always consisted of lateral temporo-occipital fast and sharp waves continually alternating with slow activity. These cycled independently in the two hemispheres and correlated with the fluctuating behavioral state. During the "postictal" phase the EEG was diffusely slow with isolated bilaterally independent temporal spikes. The key to the diagnosis of partial complex status epilepticus may be the fluctuating mental state. Recognition and prompt treatment of this disorder are important since delay could result in prolonged or enduring memory impairment.