Aspirin (I) and phenobarbital (II) in infantile co-phenobarbital powder were determined simultaneously using dual wavelength K-ratio spectrophotometry. I and II were analyzed with dual wavelength K-ratio spectrophotometry at 255, 244 and 236 nm. This method showed a mean recovery of 101.3% and a coefficient of variation of 1.6% for (I). The mean recovery and CV of II were 99.21% and 1.90% (n = 6) respectively. The method is simple, rapid and accurate.