The numeric taxonomy taking into account 80 signs has demonstrated the similarity of NAG and cholera vibrios, the average similarity coefficient exceeding 80 %. Among NAG vibrios, 53 % of the strains have been found to deviate from the central strain of V. cholerae mainly with regard to their utilization of the sources of carbon. The use of the citrate sign for the study of the biological properties of NAG vibrios is proposed.