Optical electric field induced second harmonic generation (EFISHG) measurements were employed to probe the electric field in the active layer of organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs). The OFETs used were double-layered with an active layer of pentacene/poly (3-hexyl thiophene) P3HT on SiO(2) gate insulator with Au source and drain electrodes. It was shown that SHG from the P3HT bottom layer could be selectively probed at a wavelength of 450 nm. Similarly, by using OLEDs comprised of a double layer of Tris(8-hydroxyquinolinato) aluminium (Alq(3)) and N'-di(1-naphthyl)-N,N'-diphenylbenzidine (alpha-NPD) with a device structure of indium-zinc oxide (IZO)/alpha-NPD/Alq(3)/Al, it was shown that EFISHG from the Alq(3) layer could be selectively probed at a wavelength of 1000 nm by reflective laser beam irradiation from IZO-side. The results show that the spectroscopic nature of materials allows us to selectively probe the electric field distribution in each layer of multi-layer in organic devices. (C) 2009 Elsevier B.V. All rights reserved.