  Based on the Brillouin (negentropic) principle, we answer to the question:
Does information have mass ? The obtained answer is affirmative and the mass
associated to a bit of information (which is always a positive definite
quantity) is explicitely calculated. Since the Brillouin's principle is
modified in the presence of a gravitational field, so does the mass associated
to a bit of information. Some consequences ensuing these facts, as well as the
link between radiation and information, are discussed.
