This is a seven-week study (one week screening and six weeks of study medication) where a total of 400 patients who meet entrance criteria will randomly be assigned to receive one of five groups of study treatments of either low dose haloperidol plus ACP-103, low dose haloperidol plus placebo (a substance similar to a sugar pill), low dose risperidone plus ACP-103, low dose risperidone plus placebo, or high dose risperidone plus placebo. The study will begin with with a three to seven day drug-free period followed by six weeks of a stable daily dosage of study medication. Study subjects will be treated as hospital in-patients during screening and for the first 14 days of the study. Study subjects will be closely monitored throughout the study.