We sought information worldwide on mortality according to assigned treatment in all randomised trials that began before 1985 of adjuvant tamoxifen or cytotoxic therapy for early breast cancer (with or without regional lymph node involvement). Coverage was reasonably complete for most countries. In 28 trials of tamoxifen nearly 4,000 of 16,513 women had died, and in 40 chemotherapy trials slightly more than 4,000 of 13,442 women had died. The 8,106 deaths were approximately evenly distributed over years 1,2,3,4, and 5+ of follow-up, with little useful information beyond year 5. Systematic overviews of the results of these trials demonstrated reductions in mortality due to treatment that were significant when tamoxifen was compared with no tamoxifen (p