Native low-temperature phosphorescence of mebendazole and flubendazole in ethanol is used for the determination of these imidazoles in anthelmintic preparations with wavelength maxima and detection limits of λEXC= 322 nm, λEM= 454 nm; 10 ng ml−1and λEXC= 325 nm, = λEM= 455 nm; 5 ng ml−1, respectively, with linear response up to 8 μg ml−1and 9 μg ml−1, respectively. The structural basis of these phenomena is discussed for both compounds and for related imidazoles and benzimidazoles. Apart from good sensitivity and excellent specificity offered by the technique, the use of cryogenic equipment (liquid nitrogen, special cuvettes, expensive dewar cells) implies some disadvantages for routine analyses.