Neonicotinoids are increasingly replacing the organophosphate and methylcarbamate acetylcholinesterase inhibitors which are losing their eff ectiveness due to the selection for resistant pest populations. Imidacloprid is the most important neonicotinoid with low soil persistence, high insec cidal potency and rletively low mammalian toxicity. Neurophysiological studies have confi rmed that imidacloprid is an agonist at the postsynaptic nicotinic acetylcholine receptors which stimulates the postsynaptic membrane first and then paralyses nerve conduction. In Croatia, imidacloprid is commonly used in olive growing areas, including Istria and Kvarner islands, as an eff ective mean of olive fruit fly infestation control. Once a pesticide is introduced into the environment it can be infl uenced by many physical and chemical processes. Pesticide sorption processes are undoubtedly one of the major factors aff ecting the persistence and movement in the environment. This paper describes sorption and degradation processes of imidacloprid and investigates the relationships between soil properties and sorption and degradation characteristics in four soils, representative of northern Adriatic region, namely island Krk and a coastal Istrian region. Soil content and properties (particle size, content of organic matter, acidity) have a great eff ect on sorption of imidacloprid onto soil particle. Sorption and degradation of imidacloprid increase in soil with higher clay and organic matter content and with lower acidity. The imidacloprid degradation processes are continuous, though not very rapid. According to half-life of more than 110 days, imidacloprid is classified as persistant pesticide. However, it’s liberate usage can disturb environmental cycling and thus adversely aff ect non-target organisms, including plant and animal species. In this way, imidacloprid may also impose a risk to the human health.