An ostomy pouch is provided with a normally-closed vent valve in the form of a slit-providing flexible dome secured to the interior surface of the pouch wall over a vent opening in that wall. An odor-absorbing filter extends across the vent opening (either within the dome or externally of the pouch) to deodorize gases when they are vented from the pouch. The edges of the slit seal against each other to prevent the escape of gases and protect the filter from effluent contact when the dome is in its normal unflexed state but, when the dome is squeezed between the fingers in a prescribed manner, the slit opens to permit the venting of gases from the pouch.