Over the past 2 decades, omega-3 fatty acids (n-3FAs) have been increasingly used and studied in the United States and worldwide for various medical and psychiatric indications. Numerous published clinical trials have examined applications of different n-3FA preparations, primarily in mood disorders but also in psychotic disorders, attention-deficit disorder, obsessive-compulsive disorder, and personality disorders. Focusing on clinical issues, this article reviews the impact of n-3FAs on these conditions and covers the relevant research, side effects, dosage guidelines, and drug interactions; clinicians should thus be able to better advise patients who are already taking n-3FAs or are interested in trying them.