  We review the basic ideas on the origin of cosmic rays with energy in excess
of $\sim 10^{19}$ eV, in the light of the most recent observational findings.
The limited statistics of events detected by the two largest experiments
currently operating does not allow as yet to claim the detection of the GZK
feature in the cosmic ray spectrum or the lack of it. Although extragalactic
point sources seem to be preferred on the basis of the small scale anisotropies
detected by AGASA, the possibility that UHECRs with energy in excess of
$10^{20}$ eV may be the result of the decay of supermassive particles is not
ruled out by present data. It seems clear that if we want to have a clear idea
of the origin of UHECRs, we have to auspicate the realization of larger, better
experiments, such as the ongoing Auger project and the space-borne EUSO
experiment.
