The comparative evaluation of the diagnostic value of new cholera eltor bacteriophages ctx+ and ctx-, as well as monophages X[symbol: see text]-3, 4, 5, demonstrated their high activity and specificity. Using of these bacteriophages epidemic potential of 95% Vibrio cholerae eltor strains ctx+ and 84.5% of V. cholerae eltor stains ctx- was determined. Commercial monophages X[symbol: see text]-3, 4, 5 were inferior to bacteriophages ctx+ and ctx- in their diagnostic value: only 55% of strains having gene ctxAB were found to be epidemically dangerous, i.e. 45% of strains capable of causing the disease were not detected. On the basis of the results obtained in this investigation cholera eltor bacteriophages ctx+ and ctx- were recommended for introduction into practical use, while further production of cholera diagnostic monophages X[symbol: see text]-3, 4, 5 was recommended to be stopped.