Fingerprints disclosed by cyanoacrylate on non-absorbent substrates, in order to improve readabiIity, require additional contrasting fluorescent dyes. Nile Red is one of them. Its effectiveness was tested under conditions similar to those of daily laboratory practice. The highest Nile Red fluorescence occurred in an excitation light of blue-green and a wavelength of 505nm. Spectral analysis showed that the emission of light oscillates in the wavelength of about 630nm. In order to cut off the light, longpass edge filters of the colours yellow, orange or red can be used. Filter selection depends on the characteristics of the substrate and can be chosen empirically. Nile Red fluorescence does not change over a longer period of time, which allows for the registration of fingerprints to be performed within a time convenient for the testing, without fear of losing their quality. Nile Red may be an alternative to other fluorescent dyes used for visualization in fingerprint testing.