Gene transfer by in ovo electroporation has been applied to the study of developmental biology, especially to central nervous system (CNS) development. Plasmids are injected into the neural tube of stage 10 chick embryos, and a 25-V 25-msec square pulse is applied five times. Since DNA moves toward the anode, the cathode side of the neural tube is transfected, and the cathode side is used as the control. Expression of translation product of the introduced DNA is observed 2 h after electroporation, peaks around 20 h after electroporation and then weakens. Expression is transient when plasmids are used as expression vectors, but they are very suitable for studying early developmental events (e.g., gene expression cascades or interactions). Misexpression of Pax-5 is shown as an example. Copyright 2001 Academic Press.