  Event-by-event fluctuations and correlations in azimuthal angle are currently
widely investigated in various experiments. In this paper the $\Phi$ measure
(earlier used in experiments to evaluate fluctuations in transverse momentum)
is now applied to azimuthal angle $\phi$. Properties of this $\Phi_{\phi}$
function are investigated through fast generators and with complex models such
as Pythia, Hijing, and UrQMD. Preliminary results of NA49 on $\Phi_{\phi}$ are
also presented. The system size dependence (p+p, C+C, Si+Si and 6 centralities
of Pb+Pb) at the highest SPS energy (158$A$ GeV) is shown, as well as the
energy dependence (20$A$ - 158$A$ GeV) for the 7.2\% most central Pb+Pb
interactions.
