In this work we discuss the emergence of Clinical Epidemiology with its doubly ideological nature. We begin by presenting different connotations of ideology, two of which are chosen to be discussed here. The first is the positivistic concept of ideology as the set of ideas of a given historical time; the second is the Marxist concept of ideology, as concealing relations of dominance. Under the first meaning, Clinical Epidemiology is discussed vis-à-vis ideas in force in the 1980's, giving it a predominantly post-modern character along with the load of individualism born by this word. Finally, we present the myths underlying Clinical Epidemiology, seen now according to the second meaning of ideology.