A method and device for controlling an extracorporeal blood treatment apparatus, which can be operated as a hemodialysis apparatus, hemofiltration apparatus or hemodiafiltration apparatus, are disclosed. The method and device make provision, apart from balancing the fluids as a function of the weights of the containers, for the measurement of the weight reduction or increase of at least one of the containers in the time interval in which the pump assigned to the respective container performs a preset number of revolutions or pump strokes. The change in the weight of the container for a half or one pump revolution can be determined. The delivery rate of the respective pump is ascertained from the measured weight reduction or increase in the specific time interval, thereby permitting the precise determination of the actual delivery rate of one or more pumps. The actual delivery rates of all the pumps are preferably monitored.