  We discuss the possible imprints of Strange Quark Matter (SQM) in cosmic ray
data. In particular, we investigate the propagation of SQM through the
atmosphere and discuss: i) direct candidates for strangelets, ii) exotic events
interpreted as signals of SQM and iii) muon bundles and delayed neutrons in
Extensive Air Showers. The physics and astrophysics of SQM is shortly reviewed.
We point out the possibility that extreme energy cosmic rays are the results of
the decay of unstable primordial objects. Finally, the abundance of possible
candidates for strangelets and their mass spectrum are estimated and compared
with the astrophysical limits and prospects of the possible observation of SQM
in accelerator experiments are outlined.
