We studied the growth of InGaAs nanowires on InP(1 1 1)B substrates by selective-area metal organic vapor phase epitaxy (SA-MOVPE). It was found that the initial growth rate of the nanowires depends on the supply ratio of source gas of Ga and In, and it is higher for increasing supply ratio of Ga. At the initial stage, the diameters of the nanowires were almost the same as those of the openings of the mask, indicating that the lateral growth was negligible, while the height of the nanowires increased superlinearly with time. For longer growth time, the diameter of nanowires as well as height increased linearly with time. A possible growth mechanism for such dependence on time and supply ratio of group III source gases is discussed. (C) 2007 Elsevier B.V. All rights reserved.