The present work was carried out to study the changes in the population dynamics of the sap sucking insects in the transplanted cot­ton and sown seed cotton during three successive cotton growing sea­sons (1993, 1994 and 1995) at Gharbia & Kafr El-Sheikh Governorates. To facilitate the presentation of data, each locality was discussed separ­ately. The infestation by sap sucking insects, Thrips tabaci, Aphis gassy­pii, Ernpoasca lybica and Bernisia Tabaci in cotton plants were estimated during the whole period of investigation in the three localities. Cotton grown by seeds received the highest infestation level, while cotton culti­vated by transplanting of cotton seedlings harbored the least level. However, sown seed cotton field gave more yield.