The purpose of this study is the evaluation of effectiveness of paliperidone palmitate within three different group of schizophrenia patients.

In this study, the investigators are going to examine the effectiveness of paliperidone palmitate after changing from other antipsychotics. This study design is a Prospective Naturalistic Case Series Study. The effectiveness of paliperidone would be compared within three different groups of schizophrenia. Investigators would also assess the safety during 24 weeks follow up period.

Inclusion Criteria:

• Age: 18 ~ 65
• Patient with schizophrenia according to DSM-IV criteria
• Patient have signed on the informed consent, and well understood the objective and procedure of this study.
• PANSSS total score <120
• each Score of disorganized thought, paranoia hallucinatory behavior, abnormal tbought contests < 16
• three different groups ( other antipsychotics refractory schizophrenia patitents : CGI> 4 chronic akathisia : DIEPSS overall severity >1, at least 1 month lasting symptoms poor compliance schizophrenia : CRS <3)
• Competent patient who is manage to answer the questionnaires.
• In case of female at child-bearing age, consent to use appropriate contraceptive methods(oral pill, contraceptive injection, intrauterine device, double barrier method and contraceptive patch) during entire duration of this study.

Exclusion Criteria:

• No history of antipsychotics prescription
• History of NMS(Neuroleptic malignant syndrome)
• Allergic reaction or hypersensitive reaction of risperidone or paliperidone ER
• clozapine medication within 1 month before screening
• SSRI, MAOI, TCA medication within 2 months
• Lithium, valproic acid, carbamazepine, topiramate, lamotrigine medication starting within 2 months
• patient who is supposed to be impossible to participate to this study due to clinical risk of suicide or aggressive behavior based on clinician's opinion
• current or previous history of drug depedence according to DSM-IV
• Pregnant or breast-feeding female patient
• Significant biochemical or hematological abnormality or abnormal finding of urinalysis, based on clinician's opinion
• history of cardiac disease, which is related to QT prolongation(sick sinus, complete AV block, CHF, ventricular tachycardia, hypokalemia or hypocalcemia)
• History of participating to other investigational drug trial within 1month prior to screening
• Investigator or employee at clinical trial center, personnel related to investigator or trial center on this or other study, or family of employee or investigator