Pesticide use has been associated with threats to human and ecosystem health. Inhibition of nerve function is usually the target for insect and pest control. In non-target species, there may be a: variety of additional effects of the pesticides besides nerve inhibition. Several studies have shown that pesticide exposure can cause a number of effects at the cellular level causing physiological and other disturbances in organisms. Amongst others, these include the following; endocrine disruption, oxidative stress, altered enzyme function or gene regulation. These cellular and physiological effects in individual species/organisms can manifest at higher levels within an ecosystem. Thus, reproductive and behavioural effects in organisms at a single trophic level can affect profoundly the entire ecosystem health and balance. This paper will provide an overview of these possible effects as well as show examples where they have been shown or known to operate.