Two monoclonal antibodies conjugated to fluorescein isothiocyanate (FITC) were successfully used in a direct immunofluorescence test (DIFT) to demonstrate listeria in seven samples of soft cheese whereListeria monocytogeneshad been cultured by conventional techniques. Using DIFT, listeria was not detected in 20 cheese samples from whichL. monocytogeneshad not been isolated, or was present in low numbers (90% of strains ofL. monocytogenesisolated from food and cultured on Modified McBride agar or Blood agar. Less than 10% of strains of other species of listeria would be misidentified when grown on these media. All tests were carried out within 2 h.