Myrrh (oleo-gum-resin) obtained from the stem of Commiphora molmol proved to have insecticidal activity against mosquito larvae. The oil extract of Myrrh possesses median lethal activity against 2nd, 3rd and 4th instar larvae of Culex pipiens at 0.016 x 10(2), 0.17 x 10(2) & 1.6 x 10(2) g/l respectively. While LC50 against 3rd instar larvae of Aedes caspius was 0.2 x 10(2) g/l. The oleo-resin extract showed toxicity against 2nd, 3rd, 4th instar larvae of C. pipiens recording the LC50 values of 0.06 x 10(2), 0.09 x 10(2) & 0.5 x 10(2) g/l respectively. While LC50 against 3rd instar larvae of A. caspius was 0.08 x 10(2) g/l. This plant extract has no marked toxic effect against the water bug Sphaerodema urinator (Dufor) and the water beetle Hydaticus leander (Rossi). Histological examinations of Myrrh treated mosquito larvae showed great pathological effect on their fat, muscles, gut and nervous tissues.