Quaternary prevention is a group of measures taken to prevent, decrease and/or alleviate the harm caused by health activities. Health activities not only generally produce benefits, but also harm. That is to say, although medical intervention is mainly favourable, there is a dynamic balance that requires continuous assessment of the clinical situation as naturally only those health activities that achieve more benefit than harm at the end are justified. Quaternary prevention is the avoidance of unnecessary medical activity, such as "check-ups". In another example, quaternary prevention is the recommendation of preventive measures of proven efficacy. As regards diagnosis, quaternary prevention is, for example, the avoidance of screening without foundation, such as in prostate cancer. The appropriate use of antibiotics in upper respiratory tract infections serves as an example of quaternary prevention in the field of treatment. Another example is the application of the correct rehabilitation techniques in non-specific low back pain, such as swimming and maintaining an active life as much as possible. Not to forget other important "non-classic" aspects in the elderly, such as to limit the harm that can be caused by physical movement restriction devices. These and other examples in daily practice are considered in this article to encourage the continual assessment of quaternary prevention, the classic primum non nocere "first, do no harm".