José Gutiérrez-Fernández,1 Juan de Dios Luna del Castillo,2 Sara Mañanes-González,1 José Antonio Carrillo-Ávila,1 Blanca Gutiérrez,3 Jorge A Cervilla,3 Antonio Sorlózano-Puerto1 1Department of Microbiology, 2Department of Statistics and Operation Research, 3Department of Psychiatry, Institute of Neurosciences and CIBERSAM, School of Medicine and Biohealth Research Institute (Instituto de Investigación Biosanitaria) IBS-Granada, University of Granada, Granada, Spain Abstract: In the present study we have performed both a meta-analysis and an analytical study exploring the presence of Chlamydia pneumoniae, herpes simplex virus type 1, human herpes virus 6, and Toxoplasma gondii antibodies in a sample of 143 schizophrenic patients and 143 control subjects. The meta-analysis was performed on papers published up to April 2014. The presence of serum immunoglobulin G and immunoglobulin A was performed by enzyme-linked immunosorbent assay test. The detection of microbial DNA in total peripheral blood was performed by nested polymerase chain reaction. The meta-analysis showed that: 1) C. pneumoniae DNA in blood and brain are more common in schizophrenic patients; 2) there is association with parasitism by T. gondii, despite the existence of publication bias; and 3) herpes viruses were not more common in schizophrenic patients. In our sample only anti-Toxoplasma immunoglobulin G was more prevalent and may be a risk factor related to schizophrenia, with potential value for prevention. Keywords: meta-analysis, analytical study, Chlamydia pneumoniae, herpes simplex virus type 1, human herpes virus 6, Toxoplasma gondii, schizophrenia