In a duplicated arrangement for an ATM switching system, first and second store-and-forward buffers are provided for storing and forwarding an ATM cell stream and first and second counters are responsive to a timing signal for producing a first cell count and a second cell count representative of counts of cells stored in the first and second store-and-forward buffers, respectively. A detector is provided for detecting a difference between the first and second cell counts. A buffer controller controls the second store-and-forward buffer in accordance with the difference so that the count of cells in the second buffer approaches the count of cells in the first buffer. A switching circuit normally couples the ATM cell stream forwarded from the first buffer to an output port of the ATM switching system and couples the ATM cell stream forwarded from the second buffer, instead of from the first buffer, to the output port in response to a switching command signal.