  We investigate the effect of interactions on condensate-number fluctuations
in Bose-Einstein condensates. For a contact interaction we variationally obtain
the equilibrium probability distribution for the number of particles in the
condensate. To facilitate comparison with experiment, we also calculate the
zero-time delay autocorrelation function $g^{(2)}(0)$ for different strengths
of the interaction. Finally, we focus on the case of a condensate of photons
and discuss possible mechanisms for the interaction.
