In patients with diabetes mellitus, the presence of hypertension substantially increases the risk of cardiovascular events, and reductions in blood pressure (BP) can reduce cardiovascular morbidity and mortality. Following evidence from trials randomizing patients to diastolic BP levels, previous guidelines recommended an office BP target of <130/80 mmHg in individuals with diabetes mellitus. However, the evidence for this systolic BP (SBP) target was derived from observational studies. When the results of the ACCORD-BP study showed that those individuals with diabetes mellitus and a target BP of <120 mmHg had a cardiovascular risk that is similar to those with <140 mmHg, all guidelines returned to a recommended SBP of <140 mmHg. However, the ACCORD-BP trial was limited by the low number of cardiovascular events observed, whereas the mean SBP in the 'conventional' arm was 133 mmHg. The SPRINT study, showing cardiovascular benefits in hypertensive patients without diabetes mellitus randomized to SBP <120 mmHg versus those randomized to <140 mmHg, came in contrast with the ACCORD-BP, but a detailed evaluation reveals many similarities between the two trials. Finally, the EMPA-REG OUTCOME study, with impressive cardiovascular mortality reduction with empagliflozin, suggested that reduction of SBP to around 130 mmHg is safe and might explain part of these beneficial results. In this Review, we evaluate the implications of the ACCORD-BP, SPRINT and EMPA-REG OUTCOME trials and previous studies for the optimal BP target in diabetes mellitus.