African Journal of Pharmacy and Pharmacology, 2016; 10 (28): 571-579Antimicrobial drug residues have emerged as one of the public health problems worldwide. In this study, a modified sensitive liquid chromatography mass spectrometry (LC-MS) method to detect the “Oxytetracycine” (OTC) levels in ready-to-eat beef meat in Tanzania was evaluated. Beef samples were extracted in acetonitrile in ethylenediaminetetraacetic acid (EDTA) buffer (pH 4), followed by cleaning up with Supelclean ENVI-carb active coal and a stream of nitrogen gas. The wavelength of the diode array detector (DAD) was set at 275 and 355 nm. The detection limit of the method was calculated as 18.2 ng/g and the recovery rate of OTC was 78.6%. A total of 45 ready-to-eat beef meat samples were analyzed, with 16 (35.5%) and 29 (64.5%) barbequed and boiled samples, respectively. Of the 45 samples, 35 (77.8%) samples had OTC residues while 9 (25.7%) samples had violative residue levels above the maximum residue limits recommended by the Food and Agriculture Organization and the World Health Organization. The highest concentration was 545.2 ng/g. Therefore, withdrawal period and proper use of antibiotics for animal production should be of concern as consumers are at risk of adverse effects due to consumption of unacceptable levels of drug residues and a risk of developing microbial resistance. To the best knowledge of the authors, this is the first study to evaluate LC-MS method to detect the OTC levels in ready-to-eat beef meat in Tanzania