The aim of the study was to evaluate the cytotoxicity of tulathromycin (macrolide antibiotic) on BHK-21 An30 cells and to determine the effect on FMD (Serotypes; A/TUR/11, O/TUR/07, Asia-1/TUR/15) virus propagation in vitro. In the result of MTT tests and cell culture studies, the non-toxic upper concentration of the tulathromycin limit for BHK-21 An30 cell culture was determined as 30 mu g/ml in terms of cell morphologies and numbers. The mean FMD 146S virus particle values produced in BHK-21 An30 cell cultures containing 30 fig/nil of tulathromycin were found to be 0.47, 0.57 and 0.25 mu g/ml; the mean infective titer determined as 10(7.03), 10(6.23) and 10(7.40) pfu/ml for A/TUR/11, O/TUR/07 and Asia-1/TUR/15, respectively. In the FMD virus cultures produced with medium containing penicillin-streptomycin, the mean values of 146S virus particles were determined to be A/TUR/11, O/TUR/07 and the Asia-1/TUR/15 serotypes were 0.50, 0.55, and 0.32 mu g/ml, respectively, while the mean infective titers were 10(7.46), 10(6.62) and 10(7)(.7)(3) pfu/ml, respectively. As a result, it was concluded that tulathromycin can be used as an antibiotic up to 30 mu g/ml in a BHK-21 An30 cell culture and in the production media of the FMD virus A, O, and Asia-1 serotypes.