This articles summarizes the history of Medical Research Council (MRC) acute lymphocytic leukemia (ALL) trials in adults. It includes details of the early trials UKALL I-V in which children and adults were entered. UKALL IX, XA, and XII are for those older than 15 years of age (UKALL XII has an upper age limit of 55 years). The trials are all randomized controlled trials. The treatment schedules and survival curves are shown and discussed. A total of 2565 adults were entered between 1970 and 2000, and outcomes for all of these patients are described.