The Israeli National Psychiatric Hospitalization Registry is a nationwide list of all psychiatric hospitalizations in the country and has been widely used as a source of data for psychiatric research. This study assessed the sensitivity of the diagnosis of psychotic disorders (International Statistical Classification of Diseases, 10th Revision [ICD-10] F20.0-F29.9) and schizophrenia (ICD-10 F20.0-F20.9) in the Registry. Registry discharge diagnoses of psychotic disorders (ICD-10 F20.0-F29.9) and schizophrenia (ICD-10 F20.0-F20.9) were compared with research diagnoses derived from best-estimate procedures based on Research Diagnostic Criteria (RDC) using structured clinical research interviews, hospital records, and family information. Out of 169 patients meeting RDC for psychotic disorder, 150 also had a diagnosis of psychotic disorders in the Registry, yielding a sensitivity of 0.89. Re-running this analysis for the narrow definition of schizophrenia identified 94 patients who were diagnosed with schizophrenia using RDC; 82 of those patients also had a diagnosis of schizophrenia in the Registry, yielding a sensitivity of 0.87. In 87% to 89% of cases with psychotic disorders or with schizophrenia, Registry diagnoses agreed with RDC diagnoses, a rate of agreement comparable with those of other, similar registries. Because a large number of analyses derived from this and similar national registries will be published in the coming years, this constitutes relevant information.