An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection caused by a novel phage-type (now designated EMRSA-16) occurred in three hospitals in East Northamptonshire over a 21-month period (April 1991--December 1992). Four hundred patients were colonized or infected. Seven patients died as a direct result of infection. Chest infections were significantly associated with the outbreak strain when compared with methicillin-sensitive S. aureus. Twenty-seven staff and two relatives who cared for patients were also colonized. A 'search and destroy' strategy, as advocated in the current UK guidelines for control of epidemic MRSA was implemented after detection of the first case. Despite extensive screening of staff and patients and isolation of colonized and infected patients, the outbreak strain spread to all wards of the three hospitals except paediatrics and maternity. A high incidence of throat colonization (51%) was observed. Failure to recognize the importance of this until late in the outbreak contributed to the delay in containing its spread. Key parts of the strategy which eventually contained the local outbreak were the establishment of isolation wards in two hospitals, treatment of all colonized patients and staff to eradicate carriage and screening of all patients upon discharge from wards where MRSA had ever been detected. EMRSA-16 spread to neighbouring hospitals by early 1992 and to London and the South of England by 1993. It is distinguished from other epidemic strains by its characteristic phage-type, antibiogram (susceptibility to tetracycline and resistance to ciprofloxacin), and in the pattern given on pulse field electrophoresis.