Thirty-eight cases of infections due to Neisseria meningitidis serogroup Y have been studied. They correspond to the strains sent to the Laboratory (Centre National de Référence since 1987). Their repartition was: meningitidis 9 cases, purpura fulminans (6), septicaemia (5), respiratory syndroms (11), asymptomatic carriage (4), various (3). Patients were 4 months to 86 years old. Mortality was 13.2%. One third or meningitis or meningococcemia happened in correlation with complement deficiency or splenectomy. In most of cases bacterial diagnosis was made by general laboratories but only in two cases over 38 the serogrouping Y was made.