This study is being done to evaluate the efficacy and safety of asenapine as compared to placebo in preventing the recurrence of mood episodes after stabilization of an acute/manic mixed episode in participants with Bipolar 1 Disorder. After a Screening Period, each participant will receive open-label asenapine and matching placebo for 12 to 16 weeks. Participants who meet stabilization criteria may then be randomized into one of the two study arms (asenapine or matching placebo) to receive double-blind treatment for up to an additional 26-weeks.

Inclusion criteria:

• Male, or a female who is not of child-bearing potential or who is non-pregnant, non-lactating, and is using a medically accepted method of contraception.
• Each participant must be willing and able to provide written informed consent.
• Each participant must have an identified external contact person or an identified responsible person.
• Current diagnosis of Bipolar 1 Disorder, and a current manic (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision [DSM-IV-TR^TM] code 296.4x) or mixed (DSM-IV code 296.6x) episode as determined by a structured clinical interview (Mini International Neuropsychiatric Interview [MINI]) at Screening.
• Each participant must be confirmed to be experiencing an acute manic or mixed bipolar 1 episode.

Exclusion criteria:

• Uncontrolled, unstable clinically significant medical condition.
• Clinically significant abnormal laboratory, vital sign, physical examination, or electrocardiogram findings at Screening.
• Current primary Axis I disorder other than bipolar 1 disorder.
• Meets the current DSM-IV-TR^TM criteria for substance abuse or dependence (excluding nicotine).
• Imminent risk of self-harm or harm to others.