An integer of an algebraic
number field K is called irreducible if it has no proper integer divisors in K. Every
integer of K can be written as a product of irreducible integers, usually in many
different ways. Various problems have been inspired by this lack of unique
factorization. This paper studies the question: When are the irreducible integers of K
determined by their norms? Attention is confined to the case in which K is
a quadratic field. With this assumption it is possible to give a complete
answer in terms of the ideal class group of K and the nature of the units of
K.