A laboratory culture of the boll weevil ectoparasitoid, Catolaccus grandis, was exposed to lethal and sublethal doses of insecticides and an insect growth regulator (IGR) using a spray chamber bioassay. Insecticides tested were Guthion, Phaser, Regent, Fyfanon, Baythroid, Cygon, Tracer, Methyl parathion, Orthene and Vydate. At full rates, Tracer was significantly less toxic to female C. grandis than other treatments except Phaser; Regent and Fyfanon were significantly more toxic than other treatments. Most of the chemicals tested were highly toxic to male C. grandis; Tracer was numerically less toxic. At sublethal rates, most of four selected chemicals tested were low in toxicity to C. grandis; no C. grandis pupae developed from parasitism during a 24 h treatment period with Fyfanon or Tracer. Sex ratio of progeny appeared to be unaffected by the treatments.