Objective: Aggressive behavior has been related to psychiatric patientsboth in in-patient and out-patient samples. In this study, we aimed to assess theaggression and violent behavior among hospitalized patients with schizophreniaand bipolar disorder and to study the association of aggressive behavior withmultiple variables; where a group of patients in early phase admission is comparedto a group of patients admitted for more than one month.Method: Two hundreds patients with schizophrenia or bipolar disorder receivingwere enrolled and interviewed at El Abasia psychiatric hospital about aggressiveviolent behavior within the week prior to the study visit. Presence of aggressiveepisodes, including type of aggression and severity was assessed with the ModifiedOvert Aggression Scale (MOAS). Violence was defined as a score of 3 or more inany of the MOAS subscores.Results: Prevalence of recent aggressive behavior was 44% that reached theviolent threshold. Recent aggressive episodes were more likely among patientswith a previous history of violence, substance abuse, with low treatmentsatisfaction, long admission duration, premorbid antisocial personality traits,deluded patients and with impaired insight.Conclusion: forty four percent of the studied cases showed aggressive behavior inthe week prior to assessment, despite having been compliant with their medication.Most aggressive behavior was verbal rather than physical.Significant outcomes: • Despite adherence to antipsychotic medication,admission in hospitals, a group of in-patients with schizophrenia and bipolardisorder continues to show aggressive behavior.• A past history of violence and substance abuse are among the factors associatedwith the appearance of aggressive behaviors.Limitations: A cross-sectional design does not allow a causal relationship to beestablished.