An outbreak of W135 meningococcal disease was seen in 2000 and 2001 among pilgrims returning from Saudi Arabia and their contacts. The Public Health Laboratory Service set up enhanced surveillance to monitor spread and virulence of the outbreak strain, and to collect data on case characteristics. The number of cases reported from England and Wales in 2001 was similar to the number reported during 2000, despite a change in the recommendation for pilgrims to receive quadrivalent vaccine (against serogroup A, C, W135, and Y) instead of the A/C vaccine recommended in 2000. Both the recommendation and vaccine were not available until January, 2001, and coverage among pilgrims to the Hajj 2001 was low. The case--fatality ratio was high, and sustained transmission of the virulent outbreak strain was seen. Current control policies, both in primary and secondary prevention, might need better implementation.