The work was aimed at the study of the neuraminidase activity of meningococci. The optimal conditions for detection of this enzyme in meningococci were chosen preliminarily. In experiments carried out with the observance of these conditions it was shown that meningococci of the main serological groups possessed neuraminidase activity revealed in the exponential growth phase of the microorganisms and was apparently of great pathogenetic significance providing a possibility of overcoming the physiological barrier of the host organism by the microbes.