In this paper, the simultaneous determination of paracetamol and mephenoxalone in admixture was realised by third- derivative UV spectrophotometry using a ‘zero-crossing’ technique of measurement at 239.4 nm and 249.8 nm for paracetamol and mephenoxalone, respectively. Linear correlations over the concentration ranges of 5-20 μg.mL-1 for paracetamol (r=0.9999) and 5-13 μg.mL-1 for mephenoxalone (r=0.9994) were obtained. The proposed method was applied to a commercially available tablet. The relative standard deviations obtained for 0.33% and 1.17% and, the average percentage recoveries are 99.96% and 99.46% for paracetamol and mephenoxalone, respectively. Keywords :