Silicone-polycarbonate block copolymers are provided resulting from the reaction of certain siloxy aromatic imide siloxanes or hydroxyaromatic ester siloxanes which are made by effecting reaction between an organosiloxane having terminal aromatic anhydride groups or aromatic haloacyl groups which are each attached to silicon by silicon arylene linkages with an appropriate bishydroxyarylene compounds or hydroxyarylene amino compound. The aforementioned hydroxyaromatic imide siloxanes or hydroxyaromatic ester siloxanes are then phosgenated with a dihydric phenol or an aromatic bischloroformate. The silicone-polycarbonate block copolymers have been found to be flame retardant and useful as dielectric films and membranes, and as flame retardants in aromatic polycarbonates.