We study chaos in the Hamiltonian Mean Field model (HMF), a system with man
y degrees of freedom in which N classical rotators are fully coupled. We re
view the most important results on the dynamics and the thermodynamics of t
he HMF, and in particular we focus on the chaotic properties. We study the
Lyapunov exponents and the Kolmogorov-Sinai entropy, namely their dependenc
e on the number of degrees of freedom and on energy density, both for the f
erromagnetic and the antiferromagnetic case.