The effects of fipronil and lambda-cyhalothrin, applied at rates labeled for control of the ricewater weevil, Lissorhoptrus oryzophilus, on 3 nontarget indigenous insect species in Arkansas rice are described.Three replicates of untreated control checks and fipronil- and lambda,cyhalothrin-treated plots containing 3sentinel cages each were performed. Ten 4th-stage larvae of Anopheles quadrimaculatzs, 10 adult Tropisternuslateralis, or 10 adult Notonecta indica were placed within individual cages in small rice plots treated withICON 6.2 FS (fipronil) at 0.025 lb active ingredient (Al)/acre (0.028 kg/ha) or KARATEZ 2.08 CS (tambdacyhalothrin)at 0.03 lb AVacre (0.033 kg/ha) applied over vegetation and water with a single-boom sprayer. At24 h after treatment in fipronil plots, significantly higher control of An. quadrimaculatus and T. lateralis (69and 487o control, respectively) was achieved, compared to N. indica (18%). ln lambda-cyhalothrin plots 24 hafter treatment, 100% reductions of both T. Iateralis and N. indica were highly significant (P < 0.05) from thelower level of control in An. quadrimaculatus (10%). At 48 h after treatment, no significant differences existedbetween all species within fipronil plots, with An. quadrimaculatus, T. lateralis, and N. indica obtaining 41, 10,and 1Vo control, respectively. Significantly higher (P < 0.05) control was obtained in lambda-cyhalothrin plots48 h after treatment, with 93 and 53% control of T. lateralis and N. indica, respectively, compared to 7% controlof An. quadrimerculatus. A marked difference in susceptibility was found between selected nontarget organismsused in this study. When using lambda-cyhalothrin to control adult L. oryzophilus, populations of nontargetbeneficial insects, such as T. lateralis and N. indica, could be adversely affected, whereas nontarget pestilentspecies, such as An. quadrimnculatus, could proliferate. Fipronil achieved higher percentages of control againstAn. quadrimaculatus, compared to lambda-cyhalothrin, and was less harmful to both nontarget predators.