  We start by describing the relationship between the classical prequantization
condition and the integrability of a certain Lie algebroid associated to the
problem and use this to give a global construction of the prequantizing bundle
in terms of path spaces (Introduction), then we rephrase the problem in terms
of groupoids (second section), and then we study the more general problem of
prequantizing groupoids endowed with a multiplicative 2-forms (the rest of the
paper).
