Study of some K0 rare decay processes in NA31

The large amount of data accumulated by the NA31 collaboration in order to measure Direct CP Violation in the K0 → 2 π decays can also be used to study some rare KL and KS decays. A search for the decay KL → π0e+e- is presented, together with a search for the sequence KL → π0 H0 followed by H0 → e+e-, where H0 would be a scalar boson. The prospects for studying the decays KL → π0 γγand KL → γe+e- are presented. A new limit on the decay KS → e+e- is also given