A method and apparatus for performing opportunistic refreshes of memory banks is disclosed. Refresh circuitry in a memory controller performs a refresh on each bank of a multi-bank memory at least once during a given refresh interval. At the beginning of an interval, memory banks for which there are no pending transactions (e.g., reads or writes) may be refreshed. During a first portion of the interval, refresh may be skipped for memory banks for which transactions are pending. In a second portion of the interval, refreshes are performed on memory banks that have not been refreshed during the interval, which may cause some memory transactions to be delayed.