Lithium treatment, an approach with well documented efficacy, has recently been losing its treatment value. Lithium continues working, however, for those patients for whom it was proven efficacious; that is, most patients with primary episodic affective disorders. Such responders to lithium prophylaxis can be reliably identified beforehand by a comprehensive clinical assessment. The explanation for the paradox of lithium's lost efficacy lies mostly in the educational bias against a comprehensive patient assessment, and in the shift in diagnostic fashion favouring affective disorders and the treatment methods associated with them in the clinicians' minds.