We have focussed on the largest studies and some of our interpretation of the data may initially appear counter-intuitive. Benefit must exceed harms, especially in long term prescribing, best achieved by accurate diagnosis and drug targeting, which all continue to improve. For the individual patient, harms overtake benefits as dose is increased, creating essentially a ‘J-curve’.. It has recently become apparent that the maximum useful daily maintenance dose of aspirin is substantially less than the 100-150 mg popularly prescribed, increasing persistent unintended, unfavourable effects long term. The median maximum useful dose may be nearer 50 mg, or less. Safety requires avoidance of excess dose.