Efflux is one of the major resistance mechanisms for macrolide antibiotics observed in both laboratory and clinical settings. This review summarizes the recent research on two major macrolide efflux pumps: Mef in Gram-positive organisms and Acr-AB-TolC in Haemophilus influenzae and Escherichia coli. The roles of pumps in macrolide resistance and the new advances / strategies to overcome efflux are discussed. Copyright 2000 Harcourt Publishers Ltd.