ADMINISTRATIVE FINES ARE THE MOST IMPORTANT AND MOST FREQUENTLY USED FORM OF ADMINISTRATIVE SANCTION, MORE COMMON THAN SANCTIONS INVOLVING WITHDRAWAL OF ADMINISTRATIVE PRIVILEGES OR EXPULSION FROM A PROFESSIONAL BODY. HOWEVER, IT IS NOT EASY TO DEFINE THE ADMINISTRATIVE FINE, MAINLY BECAUSE IT IS ALMOST IMPOSSIBLE TO FIT THE SPECIAL REGULATIONS GOVERNING THE APPLICATIONS OF SUCH FINES INTO A SINGLE, GENERAL THEORY. THE ADMINISTRATIVE FINE IS NOT A FORM OF COERCION; RATHER, IT IS A REPRESSIVE MEASURE REQUIRED BECAUSE AN OBLIGATION HAS NOT BEEN FULFILLED. SUCH FINES ARE NOT GOVERNED BY THE PRINCIPLES APPLICABLE IN PENAL LAW, SUCH AS GUILT, EXTENUATING CIRCUMSTANCES, AND INDIVIDUAL SENTENCING. THERE IS EXTENSIVE PROVISION FOR MONETARY FINES IN SPANISH LEGISLATION, AND FREQUENT USE IS MADE OF THESE PROVISIONS BY SPANISH ADMINISTRATIVE AUTHORITIES. ALTHOUGH SPANISH LEGISLATION DOES NOT USUALLY PROVIDE PRISON SENTENCES AS A SUBSTITUTE FOR FINES, SEVERAL PROVISIONS EXIST WHICH DO ALLOW FOR SUCH PRISON SENTENCES. HOWEVER, UNPAID ADMINISTRATIVE FINES SHOULD NOT BE REPLACED BY PRISON SENTENCES, AND IF USE OF SENTENCES IS CONTINUED, THE SENTENCE SHOULD NOT EXCEED 15 DAYS' IMPRISONMENT. ONE SOLUTION IS TO IMPOSE ADMINISTRATIVE FINES USING THE DAY-FINE SYSTEM. FINALLY, THE ADMINISTRATIVE AUTHORITIES DO NOT HAVE THE SUBJECTIVE AND OBJECTIVE COMPETENCE REQUIRED TO IMPOSE HEAVY MONETARY FINES TO PROTECT THE SOCIAL ORDER. REFERENCES ARE PROVIDED. (KCP)