Objective: Recent research on the epidemiology, clinical course, diagnosis, and treatment of bipolar II disorder (BD II) stands to have a considerable impact on clinical practice. This paper reviews these developments.Method: We conducted a Pubmed search, focusing on the period from January 1, 1994, to August 31, 2004. Articles deemed directly relevant to the epidemiology, course, diagnosis, and management of BD II were considered.Results: The prevalence of BD II is likely higher than previously suggested. Systematic probing for particular clinical features and use of screening tools allow for a more timely and accurate detection of the disorder. There is a paucity of good quality data to guide clinicians treating BD II.Conclusion: Significant progress has been made in clarifying diagnostic and treatment issues in BD II. Neither strong nor broad treatment recommendations can be made; a cautious interpretation of available data suggests that lithium or lamotrigine are fairly reasonable first-line choices. More well-designed studies with larger samples are needed to improve the evidence base for managing this disorder. [ABSTRACT FROM AUTHOR]