A toilet ventilation system including a toilet bowl having a plurality of ports for directing water into an interior of the bowl. The toilet includes a tank for holding water, and an interior passageway for conveying water from the tank to the ports of the toilet bowl. The toilet also includes an overflow tube mounted within the tank which is in fluid communication with the interior passageway. The toilet further includes a ventilation port in fluid communication with the interior passageway. A valve structure allows water to flow from the tank to the interior passageway of the overflow tube, but prevents air from being drawn from the tank into the interior passageway through the overflow tube.