In 1998 S. Smale suggested to consider a restriction of the second part of the 16th Hilbert problem to Lienard equations. In this talk we will show how to get some explicit upper estimates for the number of limit cycles of (generalized) Lienard equations. There are two different parts of this work. In the first part we deal with some geometrical properties of the phase space. The second part is an application of the theorem of Ilyashenko and Yakovenko (that binds the number of zeros and the growth of a holomorphic function) to a Poincare map.