A simple mechanism is proposed to explain and predict the bubble and slug lengths in Taylor (slug) flow in microchannels. The results obtained using the proposed approach are in good agreement with a correlation based on numerical experiments [Qian, D. and Lawal, A., 2006, Numerical study on gas and liquid slugs for Taylor flow in a T-junction microchannel. Chem Eng Sci, 80: 7609-7625] and available experimental data. (c) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.