Thiamethoxam is the first commercial neonicotinoid insecticide from the thianicotinyl subclass. It was discovered in the course of our optimisation program on neonicotinoids started in 1985. Novel variations of the nitroimino-heterocycle of imidacloprid led to 4-nitroimino-1,3,5-oxadiazinanes exhibiting high insecticidal activity. Among these, thiamethoxam (CGA 293433) was identified as the best compound and selected for worldwide development. The compound can be synthesised in only a few steps and high yield from easily accessible starting materials. Thiamethoxam acts by binding to nicotinic acetylcholine receptors. It exhibits exceptional systemic characteristics and provides excellent control of a broad range of commercially important pests, such as aphids, jassids, whiteflies, thrips, rice hoppers, Colorado potato beetle, flea beetles and wireworms, as well as some lepidopteran species. In addition, a strong preventative effect on some virus transmissions has been demonstrated. Thiamethoxam is developed both for foliar/soil applications and as a seed treatment for use in most agricultural crops all over the world. Low use rates, flexible application methods, excellent efficacy, long-lasting residual activity and favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.