Fipronil, discovered by Rhone-Poulenc scientists in 1987, is the first in a whole new class of foliar and soil insecticides called the phenyl pyrazoles. During the past eight years, fipronil has been evaluated on more than 250 insect pests on some 60 crops worldwide; the primary agricultural opportunities include cotton, rice, banana, corn, citrus, sugarcane, potato and sugar beet. The first commercial launch of fipronil was in Vietnam (rice pests) and Colombia (cotton boll weevil) in 1993. With more than five years of experience for boll weevil control in Colombia, two of them commercial, the significance of fipronil as a tool for boll weevil management is now clear. 65-70 g ai/Ha of fipronil (as Regent® 200 SC) provides superior and long residual control of boll weevil, Anthonomus grandis, (Boheman) generally reducing the number of applications required during a season by two or more compared to other commercial products. Fipronil rapidly breaks the weevil lifecycle, resulting in reduced fruit damage and significantly higher cotton yields. A secondary benefit from using fipronil for boll weevil control is suppression of other insect pests. Even at low application rates, fipronil applied alone has been shown to suppress Heliothis virescens, Spodoptera spp. and Alabama argillacea damage. When used in combination with an IGR or thiodicarb (as Larvin® 375), fipronil has clearly demonstrated superior Heliothis virescens and Alabama argillacea control compared to a mixture of endosulfan and IGRs. Low application rates, excellent yield responses and reduced number of applications make fipronil a highly economically favorable tool for boll weevil control compared to commonly used commercial products such as methyl parathion and endosulfan. Field and laboratory studies on beneficial insects have provided encouraging results, indicating that fipronil is softer on beneficial insects than methyl parathion and endosulfan. The benefits of fipronil for Anthonomus grandis control have also been demonstrated in Venezuela, Guatemala, Paraguay, Peru, Mexico and the USA, and against A. vestitus in Peru. Fipronil is now registered for boll weevil control in Venezuela, Guatemala, Paraguay and Puru; registration in the US is planned for the 1998 cotton season. The commercial success of fipronil in Colombia after only two years is a testament to its premium level of performance.