The residue depletion of oxytetracycline (OTC) from muscle tissue of cultured shrimp (Penaeus vannamei) was evaluated. OTC was measured using high performance liquid chromatography (HPLC) and a microbial receptor assay. Samples were taken on days 7, 14 and 21 during the treatment and 23, 25 and 28 after the treatment. OTC was detectable in all groups after 7 days depletion time at concentrations of 0.28, 0.19 and 0.05 μg/g for diets containing 500, 250 and 100 mg/kg OTC, respectively. Results by the microbial receptor assay were in good agreement with those by HPLC.