Abstract: An apparatus and method for measuring the error rate of a wireless device, such as a WLAN card, comprising a signal generator, a signal receiver and the device under test configured to transmit and receive frames. The signal generator transmits frames to the device under test, which sends an acknowledgement if a frame has been validly received. A controller counts valid acknowledgements received and pseudo-valid acknowledgements sent by the device (up to a maximum of one per transmitted frame). The pseudo-valid acknowledgements may be corrupted acknowledgements received by the signal receiver or signals resembling an acknowledgement detected during a time when an acknowledgement is expected. Thus a frame error rate is computed based on the total number of valid and pseudo-valid acknowledgements compared to the total number of frames sent.