This dissertation explores the use of free liquid jets for high speed immunoassays. Fluorescence and surface-enhanced Raman scattering (SERS) are employed for readout. A free liquid jet was first used to speed incubations in an assay for rabbit IgG with fluorescently-tagged anti-rabbit IgG as label. Theoretical underpinnings of this method are put forward to explain the basis for the dramatic reductions in sample and label incubation times through comparisons in surface accumulation. Immunoassay incubation by free liquid jet was extended to detect a simulant for biowarfare agents with SERS detection. The theoretical model of accumulation via quiet solution and free liquid jets is extended to account for the observations in sample capture and labeling efficiency therein. The SERS-based immunoassay with free liquid jet for sample delivery was also applied to detect porcine parvovirus (PPV), an analyte with larger size than those previously used. The successful capture of PPV through jet incubation led to a study of SERS label size and its effect on labeling by jet. Finally, extremely sensitive detection of pathogenic bacteria, E. coli O157:H7, was demonstrated by free liquid jet. The low levels of detection achieved in this assay were attributed to an enhancement mechanism in the way of detection of protein shed from the cells. This was supported by scanning electron microscopy (SEM), used to image the immunoassay substrate surface.