A simple, sensitive and reliable HPLC-MS/MS and HPLC-UV methods were developed and validated for Cis- and Trans-Cefprozil diastereoisomers determination in human plasma. The plasma samples subjected to protein precipitation after the addition of cephalexin as internal standard. Chromatographic separation was achieved using Waters Xbridge C18 column 5µm, 4.6×150mm maintained at 25° C. The HPLC-MS/MS method utilized MRM transitions; 390.1 to 208.1 and 348.1 to 158.2 for Cefprozil and cephalexin detection respectively, while the wavelength 292 nm was used for the UV detection. Both methods provided good linearity for Cis- and Trans- diastereoisomers within the ranges of 0.05-10.00 and 0.02-1.00 μg/ml respectively. Methods were validated and applied successively to study the bioequivalence of two Cefprozil pharmaceutical products. The maximum plasma levels detected (Cmax) of Cefprozil for the brand and generic products were, respectively; 10.0 and 9.9 μg/ml using the HPLC-MS/MS method compared to 10.5 and 10.6 μg/ml using the HPLC-UV method. The pharmaceutical products were found to be bioequivalent after analysis using both methods. The reference product pharmacokinetics data were statistically compared over the two methods and insignificant P-values were obtained. This comparison considered as extra prove for both methods reproducibility, reliability and ability to quantify Cefprozil diastereoisomers in human plasma.