The purpose of this study is to examine the effects of the neurosecretory material (NSM) in median neurosecretory cells (MNC) on reproduction of endoparasitic Pimpla turionellae L.. For this purpose, the egg maturation and amount of the NSM in MNC of the insects were examined by the serial cross sections of the brain. Egg maturation was determined by measuring the terminal oocyte length in the ovariole. The sections of insect brains were stained by paraldehyde fuchsin to determine the amount of the NSM in the neurosecretory granules of the MNC. The amount of the NSM in MNC was at a certain level in the first day of egg development. While terminal oocyte was reaching the maximum length, amount of NSM in MNC decreased the minumum level. During the egg laying phase, the amount of the NSM in MNC reached the maximum level. These observations give us the idea that the neurosecretory material in median neurosecretory cell of this insect may be related to the egg development.