Evaluation of human exposure to environmental chemicals is a key goal of analytical efforts. Evaluation of human exposure requires that large numbers of samples be run with a high degree of accuracy and precision and then correlated with health effects and potential exposure. Immunoassays are valuable in such studies. We are moving conventional enzyme linked immunosorbent (ELISA)-based assays toward other formats which promise to be faster, better and cheaper than laboratory-based assays. Development of improved assay throughput and sensitivity includes substitution of enzyme labels with fluorescent nanoparticles probes or luminescent acridinium labels together with the use of automated clinical-type analyzers, immunosensors or microchips with flow-through systems. Miniaturization of immunoassays for pesticide metabolites is achieved by developing completely new formats using laser-induced fluorescence detection in microdroplets and microarray assays based on microcontact printing of proteins and confocal microscopy imaging. Lanthanide chelates and lanthanide oxide nanoparticles are successfully used as reporters in the immunoanalysis of the herbicide atrazine and the common pyrethroid insecticide metabolite 3-phenoxybenzoic acid. The use of europium oxide nanoparticles in competitive fluorescence immunoassays results in increased assay sensitivity compared to the conventional 96-well plate enzyme assays. We engineered a novel type of nanoparticle that has both phosphorescent and magnetic properties. The synthesis method offers low-cost, high-rate synthesis allowing a wide range of biological applications of magnetic/fluorescent core/shell particles. We demonstrate an immunoassay using the magnetic and phosphorescent properties of the particles for separation and detection purposes.