Fluoresczently labelled molecules are widely used in analytical measurements on account of the very high sensitivity which can be achieved in favourable circumstances. In particular, fluorescent labels are becoming important as replacements for radioisotopes in a variety of applications. The ultimate sensivity of such measurements depends on the ability to eliminate interferences from background fluorescence andscattered light. One very effective means to achieve this sensitivity is to use fluorescent lables with long emissive lifetimes, which can readily be distinguished from short-lived background emission. Recently developed technology has simplified lifetime-resolved fluorescence measurements to a level where these can be used routinely in analytical measurements. Unfortunately, many labels with long fluorescence lifetimes are particularly susceptible to fluorescence quenching by environmental influences. To avoid this we propose to develop a novel time-resolved fluorescence detection system designed for use with specially developed surface-engineered fluorescent labels of near-colloidal size. Such nanoparticles provide a protective matrix within which fluorescent species of long lifetime emit with very high efficiency. The proposed technology would expand the analytical applications of lifetime-resolved fluorescence detection. In addition, the nature of the measurement allows very low cost solid-state excitation and detection systems to be used in a compact format while maintaining very high sensitivity.