LCx amplification assay, usually employed to detect Mycobacterium tuberculosis complex in respiratory specimens, was evaluated by comparing the results it gave with those obtained using Lowenstein-Jensen solid medium and pathological findings on 55 lymph nodes from cattle with positive and 10 lymph nodes form cattle with negative skin tests for tuberculosis. Fifty-three cultures (51 and 2 respectively) were positive for Mycobacterium bovis while the results for the LCx assay and the histological method were positive in 48 (45 from skin test positive and 3 from skin test negative) and 24 (20 from skin test positive and 4 from skin test negative) samples, respectively. The results obtained with the LCx assay, compared with the bacteriology, regarded as the gold standard among the diagnosis methods, gave a specificity of 91.6% and sensitivity of 90.5%. Although the sensitivity of LCx was sub optimal, DNA of M. bovis was detected in 81.8% of the skin test-positive animals. Amplification assay could rovide a rapid and reliable tool for detecting tuberculosis in cattle.