We present here the growth of GaAs, InAs and InGaAs nanowires by molecular beam epitaxy. The nanowires have been grown on different substrates [GaAs(0 0 1), GaAs(1 1 1), SiO2 and Si(1 1 1)] using gold as the growth catalyst. We show how the different substrates affect the results in terms of nanowire density and morphology. We also show that the growth temperature for the InGaAs nanowires has to be carefully chosen to obtain homogeneous alloys.