In this paper we present some applications of maximum entropy techniques in atmospheric physics and in environmental problems. In the first case we analyze the possibility of using entropy as a regularization operator in the solution of Fredholm integral equations. We discuss in detail the inversion of aerosol size distributions from ground measurements. The results of regularization by entropy are compared with those obtained using the derivatives of the unknown function, as usually suggested in the literature [1]. In the second case we use maximum entropy techniques in statistics in order to study the behaviour of an area perturbed by pollution problems (thermoelectric plant) using the biological composition species as an indicator of environmental conditions. We show that statistics derived from entropy principles are very suitable to delineate homogeneous areas and transition areas which require careful monitoring.