A growing body of evidence supports preventive interventions in asymptomatic adults. Primary prevention, which includes counselling (in particular for smoking cessation) and review of immunisation status, has been shown to be more cost-effective than secondary prevention. Evidence supports screening for hypertension, hyperlipidaemia, cervical cancer, colorectal cancer, breast cancer and obesity. Screening for lung, pancreatic and ovarian cancer has no effect on outcome and should not be performed. Controversial preventive interventions include general screening for diabetes mellitus, thyroid disorders and prostate cancer. Physicians should be aware of a possible hidden agenda in patients presenting for a checkup.