RESULTS — There were 13,344 patients alive in January 1993 who were diagnosed with type 2 diabetes in Tayside,Scotland, U.K., before 2004, of which 12,255 were eligible for the study. We identified 5,183 patients who received a first prescription for metformin after 1994 and selected 4,944 for whom there was no cancer diagnosis prior to metformin use. The remaining patients were 5,883 patients who received no metformin prescriptions between 1993 and 2004 and 1,189 patients who received a prescription for metformin in 1993.These latter patients were excluded as the date of starting metformin was unknown (no prescribing data available prior to 1993). Figure 1 shows how patients were selected for the study.