Diarrhoeal disease caused by enteropathogenic E. coli (EPEC) is dependent on a delivery system that injects numerous bacterial ‘effector’ proteins directly into host cells. The best-described EPEC effectors are encoded together on the locus of enterocyte effacement (LEE) pathogenicity island and display high levels of multifunctionality and cooperativity within the host cell. More recently, effectors encoded outside the LEE (non-LEE effectors) have been discovered and their functions are beginning to be uncovered. The recent completion of the EPEC genome sequence suggests its effector repertoire consists of at least 21 effector proteins. Here, we describe the genomic location of effectors and discuss recent advances made on effector cellular function as well as their role in the infection process.