We have recently reported that memantine has a clinically relevant antimanic and long-lasting mood-stabilizing effect in treatment- resistant bipolar disorders, both as augmenting agent and as a monotherapy. Moreover, we observed an acute antimanic and sustained mood-stabilizing effect also in "naïve" bipolar type I disorder. Here we report a case history of a young woman suffering from bipolar type II mood disorder, associated with a very severe eating disorder, showing an acute antimanic and a long-term prophylactic effect of memantine on bipolar disorder and comorbid eating disorder.