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Background/Objectives Bilateral Independent Periodic Discharges (BiPDs), previously termed BiPLEDs, are a distinct EEG pattern that was described over four decades ago, but the aetiology and prognosis remain inadequately defined.Methods Patients with BiPDs were identified via the EEG databases of two major teaching hospitals. Clinical and imaging data were analyzed.Results Forty patients with BiPDs were identified between 2003 and 2024 (72% male, median age 67, with 60% aged >65 years). A prior history of epilepsy was identified in 10% of patients. Hypoxic-ischemic encephalopathy was the most prevalent aetiology (20%). Herpes simplex and other infectious and autoimmune encephalitis comprised 17% of patients, with the remainder related to trauma, malignancy, and metabolic processes. Electrographic seizures during the EEG occurred in 30% of patients, with 10% experiencing clinical seizures during EEG recording. Mortality at 30 days was 50%, with 80% of patients dying within 90 days. The mean age of deceased patients was 60 years. Among patients with hypoxic-ischemic encephalopathy, 100% died within 30 days. In contrast, no patients with BiPDs related to autoimmune encephalitis or an exacerbation of prior epilepsy died.Conclusion BiPDs are a marker of a severe acute central nervous system insult and are associated with a high mortality rate, particularly in older patients and those with hypoxic-ischemic aetiologies.