A method of detecting mildew on textiles was developed based on the detection of fluorescence from the substrate under the ultraviolet (UV) radiation. Fluorescence microscopy was used to detect nine standard textile biodeteriogens. Eight of the nine biodeteriogens produced some autofluorescence when exposed to blue light excitation. Differences in intensity of fluorescence indicated chemical differences. The findings partially explain the association between mildew-damaged textiles and fluorescence.