Experiments are carried out to study liquid–liquid two-phase flow patterns in Y-junction microchannels etched in glass chips. The liquid–liquid test systems used in the experiments are the three standard test systems recommended by the European Federation of Chemical Engineering (EFCE) for extraction studies. Four different flow patternsslug flow, slug and droplet flow, droplet flow, and parallel floware observed. Effects of microchannel diameter, flow rate, interfacial tension of the liquids, and hydrophobicity of channel wall on two-phase flow patterns have been studied, and flow regime maps are presented and discussed.