Serogroup B isolates of Neisseria meningitidis recovered from 278 patients with systemic disease in the Netherlands between 1958 and 1986 were analyzed with respect to serotype and multilocus enzyme genotype. Of the isolates, 28% wereserotype 2b and 53% were neither serotypeable nor serosubtypeable. There were 145 distinct multilocus genotypes (electrophoretic types, ETs), with up to 31 isolates belonging to the same ET. Temporal changes in the genotypic composition of meningococcal populations in the Netherlands were demonstrated by the recent occurrence of disease caused by three clone lineages, I, III, and VI, that were not found before 1975. The epidemic of 1966–1967 and the hyperendemic wave of 1972 were caused, in large part, by two closely related but distinct clones of serotype 2b isolates, ET-ll and ET-17, respectively. Deviations in male-to-female ratio and age distribution of patients were observed for disease caused by isolates of individual clone lineages.