Post-mortem human brain studies allow clear regional localization of changes in stable components of the endogenous cannabinoid system. There are three methods that have been used to date to quantify changes in the CB1 receptor in schizophrenia: in-situ radioligand binding and quantitative autoradiography; in-situ hybridization; and immunohistochemistry. In summary, the majority of studies demonstrate changes in CB1 receptor protein density in some brain regions in post-mortem tissue from subjects with schizophrenia. A number of factors need to be considered in interpreting these studies. A possible important factor is the role of long term antipsychotic medication in influencing CB1 receptor levels. It is possible that exogenous cannabinoids may influence CB1 receptor levels in schizophrenia. The changes in CB1 receptor in schizophrenia need to be definitively localized and quantified before speculating as to the possible implications for the pathology of schizophrenia.