Three new spectrophotometric methods are described for the determination of oxfendazole and oxyclozanide in their binary mixture: first derivative spectrophotometry, ratio spectra derivative and Vierordt's method. The procedures do not require any prior separation. In the derivative spectrophotometry, the dA/dλ values were measured at 308.8 nm for oxyclozanide and at 326.0 nm for oxfendazole in the first derivative spectra of the mixture. The calibration graphs were linear in the range 8-32 μg.mL-1 for oxyclozanide and 4-16 μg.mL-1 for oxfendazole. In ratio spectra derivative spectrophotometry, the calibration graphs for 4-32 μg.mL-1 oxyclozanide and for 2-16 μg.mL-1 oxfendazole were obtained by measuring the signals at 255.0 and 273.1 nm for oxyclozanide and at 281.8 and 304.6 nm for oxfendazole. In Vierordt's method, A11 (%1, 1 cm) values of oxfendazole and oxyclozanide were determined at 308.7 and 326.1 nm in the zero-order spectra. The amounts of both compounds were calculated by using the A11 (%1, 1 cm) values. The methods were successfully applied to a veterinary formulation for determination of both active compounds. © Elsevier.