[en] The medical exposure Directive of 1984 was updated in 1997 (EURATOM 97/43) and should be implemented into national legislation before May 2000. Need for harmonisation exists in Europe, as differences in the application of ionising radiation exist throughout European countries and social mobility of the population is increasing. The context of the justification/optimisation process as well as specific characteristics of national health legislation and Social Security legislation and their impact on radiation protection of the patient, are presented. Existing differences in the justification process throughout Europe are; (i) prescribing process of the X ray examination, training of the prescriber; (ii) auto-referral; (iii) economic situation in the member states. The optimisation process is mainly sensitive to: (i) 'culture' of radiation protection in each national medical community; (ii) training; (iii) technical and clinical audits; (iv) quality assurance. (author)