A device for collecting oral fluid includes a mouthpiece with a fluid inlet connected to a collection chamber. The collection chamber includes a collecting vessel, a venting outlet, and an access port. The venting outlet may be covered by a liquid-impervious or resistant membrane, such as a hydrophobic membrane, and the access port is suitable for removing some or all of the collected fluid. This arrangement allows a saliva donor to continuously spit saliva and blow air into the closed collection chamber, without pressure build-up in the collection chamber, and without the need for the donor to release from the device until the desired oral fluid volume is collected. A valve, including a check valve may be in the saliva flow stream and baffles and structure creating a tortuous path may be utilized to keep saliva away from the membrane.
