A method and tester for determining the error rate of a mobile radio device with variable block allocation is provided. Transmission blocks are sent to a mobile radio device to be tested. The mobile radio device to be tested receives and evaluates the transmission blocks and transmits a first and a second qualifier (ack, nack), respectively, for every transmission block correctly or not correctly evaluated. The number of transmission blocks sent to the mobile radio device to be tested and that are not correctly evaluated by the device is determined, and an error rate is determined, the number of transmission blocks being variably set by multiblocks that address the mobile radio device to be tested between one transmission block per multiblock and all transmission blocks of the multiblock and one multiblock comprising a fixed number of transmission blocks.