A description is given of a major outbreak of isoniazid monoresistant tuberculosis (TB) chiefly in north London, including prisons. The earliest case was diagnosed in 1995 with most cases appearing after 1999.
HPA Mycobacterium Reference Unit, King's College Hospital (Dulwich), Guy's King's and St Thomas' Medical School, London SE22 8QF, UK. m.c.p.r@doctors.org.uk