The performance and characteristics of amperometric enzyme-based biosensors for environmental monitoring are described in detail in Chapter 1. The concept of enzyme inhibition is also outlined including detailed theoretical evaluation of inhibitor type. The inhibition of one or more enzymes in a metabolic pathway can have detrimental effects in vivo. Inhibitors range from food constituents, pesticides, halide, azide and cyanide compounds, drug and related therapeutic agents, respiratory poisons, oxides and peroxides. In Chapter 2 the use of screen printing is described as a disposable tyrosinase based biosensor for the monitoring of selected inhibitors. The characterisation and attractive performance of single use inhibitor biosensor strips is presented. Exploitation of mushroom tissue electrodes for the convenient monitoring of tyrosinase inhibitors is also outlined, including detailed elucidation of inhibitor type using native tyrosinase enzyme. Tyrosinase as a polyphenol oxidase is also an ideal candidate for the biosensing of phenolic compounds. The use of several hydrocarbon pasting liquids for improved tyrosinase-based carbon paste phenol biosensors is demonstrated in Chapter 3. Much interest has evolved in recent years on the use of sol-gel glasses in sensor manufacturing. Chapter 4 addresses this area with a sol-gel carbon composite electrode as an amperometric detector for catecholamines in liquid chromatography. An example of a sol-gel amperometric biosensor for the analysis of phenolics is also described. The most recent advancement in amperometric biosensing models, has been the proposed use of cytochrome P450 enzyme for environmental monitoring. Cytochrome P450s are heamthiolate monooxygenase enzymes that result in the hydroxylation of a wide range of substances. This novel biosensing technique is presented in Chapter 5 in relation to the encapsulation of the P450 enzyme along with membrane vesicles, within a methyltriethoxysilane gel. The behaviour of this biosensor for the analysis of polyaromatic hydrocarbons is evaluated. The thesis concludes in Chapter 6 with a critical assessment of the work performed there-in, along with suggestions for future work.