The role and importance of the blader hibiscus weed plant, Hibis­cus trionum L., as a source of economic pests infesting cotton plants, was studied at Sakha Agricultural Research Station, Kafr El-Sheikh Gov­ernorate during the two cotton growing seasons 1999 and 2000. Nine insect species; 7 pest and 2 predatory species were recorded on the weed plants. The three pest species: Oxycarenus hyalineipenne (Costa), Bemesi tabaci (Genn.) and Aphis gossypii (Glov.) occurred in relatively high numbers, while the others: Earias Msulana .(Boisd.), Thrips tabaci Lind.. Spodoptera litteralis (Boisd.), Empoasca &Dice (de Berg.) and the two predatory species; Scymnus interruptus (Goez.) and Orius albidipen­nis L. were found in relatively low numbers. H. trionum acted as a source of infestation with some economic cotton pests, particularly 0. hyalini­ponnes, A. gossypii, B. tabaci, and E. insulana when grown in cotton fields. The pests occurred on the weed earlier than on the cotton plants. Accordingly, it is recommended to get rid of the weed as early as possi­ble whenever it occurs.