The study involves two phases. Outpatients with AD who meet inclusion/ exclusion criteria enter Phase A, the 20 week open acute treatment phase that uses a flexible dose regimen of haloperidol 1-5 mg daily. Haloperidol is started at an oral dose of 1 mg daily, with subsequent dose titration in 1 mg increments until the optimal dose is reached, i.e., optimal trade-off between efficacy and side effects. At the end of Phase A, patients who do not meet criteria for clinical response exit the protocol and is treated openly with alternative medications.