We demonstrate the ability of the reversible addition-fragmentation chain transfer (RAFT) process to produce well-defined block co-oligomers for which each block has a narrow molecular weight distribution and degrees of polymerization ranging from 2 to 33. We exploit RAFT versatility to control the structure of the co-oligomers and produce amphiphilic block co-oligomers of styrene, acrylic acid and ethylene glycol. A detailed study shows that the amphiphilic diblock co-oligomers self-assemble in solution and form micelles or particles, depending on the hydrophobicity of the diblock. These oligomers present an excellent alternative to traditional amphiphilic molecules, by combining the properties of polymers with those of single molecule surfactants. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 187-198, 2012