Abstract: Data processing based apparatus makes an automated trading market for one or more securities. The system retrieves the best obtaining bid and asked prices from a remote data base, covering the ensemble of institutions or others making a market for the relevant securities. Data characterizing each securities buy/sell order requested by a customer is supplied to the system. The order is qualified for execution by comparing its specifics against predetermined stored parameters. The stored parameters include the operative bid and asked prices, the amount of stock available for customer purchase or sale, and maximum single order size.Once qualified, the order is executed and the appropriate parameters are updated. The system provides inventory (position) control and profit accounting for the market maker. Finally, the system reports the executed trade details to the customer, and to national stock price reporting systems.