Insect growth regulators (IGRs) of the juvenile hormone type alter physiological processes essential to insect development and appear to act specifically on insects. Three natural juvenile hormones have been found in insects but not in other organisms. Future use of antagonists or inhibitors of hormone synthesis may be technically possible as an advantageous extension of pest control by IGRs. A documented survey of the properties, metabolism, toxicology, and uses of the most commercially advanced chemical, methoprene, shows it to be environmentally acceptable and toxicologically innocuous. Derivation of its current use patterns is discussed and limitations on these are noted. Residue levels and their measurement in the ppb region have allowed exemption from the requirement of tolerances in the EPA registered use of methoprene for mosquito control. Tolerances for foods accompany its fully approved use for control of manure breeding flies through a cattle feed supplement. The human health effects of using this chemical appear to be purely beneficial, but further advances through new IGR chemicals appear unlikely without major changes in regulatory and legislative policy.