Double - Blind, Randomized, single centered study. The purpose of this study is to assess the feasibility of minocycline vs. placebo, added to atypical antipsychotic medications, for positive symptoms in adults suffering from schizophrenia.

Inclusion Criteria:

• Men and women 20-65 years of age.
• Primary DSM-IV diagnosis of Schizophrenia based on SCID for schizophrenia and confirmed by two senior psychiatrists.
• Patients who scored "moderate" (4) or higher on at least three of seven positive items in PANSS
• Initiated on treatment with atypical anti-psychotic medication.
• Capable and willing to provide informed consent
• Able to adhere to the treatment schedule
• Able to read, hear, write and speak the local language.
• Has signed a written informed consent to participate in the study

Exclusion Criteria:

• Patients with acute, unstable, significant, or untreated medical illness besides schizophrenia including alcohol and drug dependence, or depression.
• Current suicidal ideation or history of a suicide attempt in the past 3 years
• Known or suspected pregnancy or women of childbearing potential and not using a medically accepted form of contraception when engaging in sexual intercourse. or women who are breastfeeding
• Subjects who were taking a known contraindication to minocycline treatment.
• Subjects who had received treatment with minocycline or β-lactam antibiotics in the preceding half year before study entry.
• Subjects who were under compulsory hospitalization.