Pmr technique has been used to determine quantitatively ampicillin and dicloxacillin. This was conducted by the use of maleic anhydride as internal standard and by measuring the integrating response of the sharp singlet, the two hydrogen of maleic anhydride that appear at 8=6.55 ppm and compared to the peak height of the two aromatic hydrogen groups of ampicillin and dicloxacillin that integrate for 8H atoms that appear as doublet at 8.0 ppm. The ampicillin content of the mixture is being determined by measuring the integrating response of the peak height of the doublet of the 7H of ampicillin. The mean % recovery t S.D. were (101.15 t 1.63),(99.6±2.92) and (99.62±5.86) for ampicillin, dicloxacillin and total respectively.