Off-label medication use is common practice, particularly in difficult to treat patients who have already tried commonly accepted medication unsuccessfully. Health authorities try to regulate this practice to protect the patient's safety and to prevent over consumption of new and more expensive drugs. Justified off-label drug use requires a thorough assessment. Physicians, in cooperation with formulary committees, need tools to structure this assessment. The evaluation algorithm for off-label prescription we present here, to be used after identification of a planned off-label application, consists of four steps. Step 1 indicates the extent of the problem and the need for further investigation. Step 2 is the decisional process evaluating the necessity of off-label use in identified prescriptions and confirmation as to what extent it needs further investigation. In step 3, the scientific knowledge to support the proposed off-label use is gathered in a short or extensive evaluation trajectory. The short trajectory consists of assembling the information approved in other countries or in accepted guidelines and textbooks, whereas the extensive trajectory is necessary when the indication, route, or formulation is not approved nationally or internationally. Assessment needs to be based on a literature research on the clinical and pharmacological information of the product. Step 4 is the acceptance or rejection of the off-label use of the drug for the indication at hand. Those four steps need to be carefully documented. Treatment outcome will then be closely monitored, documented, and made available to professionals, thus allowing for regular update of recommendations. This algorithm can help formulary committees to develop a strategy for evaluating off-label prescriptions in well-defined conditions, and help healthcare providers to develop protocols and guidelines.