AMCA Streptavidin is produced by conjugating streptavidin with a coumarin fluorescent dye, 7-amino-4-methylcoumarin-3-acetic acid. This derivative excites in the ultraviolet (350 nm) and emits in the visible (450 nm) producing an intense blue fluorescence. Most paraffin-embedded tissues have little autofluorescence under those conditions. AMCA Streptavidin may provide an advantage in many labeling situations over conjugates of fluorescein and related dyes. AMCA Streptavidin can be used on frozen or paraffin-embedded sections as a single label or in combination with other fluorescent conjugates for multiple labeling studies.