Abstract: A mixing valve for hot and cold water has two control levers for single hand operation each governing the position of a valve plug. The one lever controls the flow rate of the hot water and the other the flow rate of the cold water. The temperature of the mixed water is regulated by change of the relative positions of the levers and its flow rate is controlled by movement of the levers in unison. Such movement will leave the temperature unaffected because the levers actuate the plugs over cam means and the control surfaces between those means and the plugs yield a logarithmic relationship between the flow area at each plug and the corresponding lever movement.