A method for routing a financial instrument order incorporating dark pools and at least one electronic communication network (ECN) or exchange. The financial instrument order includes an identification of a financial instrument, a bid or ask price, and a number of units to be traded. A ping order of the dark pools is determined. The financial instrument order is routed to a top dark pool as an immediate or cancel order. If the financial instrument order is not complete, the ping order is updated by removing the top dark pool. If any dark pools remain in the updated ping order, the financial instrument order is routed to the next dark pool. This process continues until all of the dark pools have been pinged or the financial instrument order is complete. If the financial instrument order is not complete, the financial instrument order is routed to the ECN or exchange.