Since the first observation of antihydrogen in 1995 at CERN there has been a rapid development in this field, both in the experimental techniques and the number of experiments. Within 7 year cold antihydrogen had been produced (Nature **) and presently the antiatoms are routinely trapped (nature and anature physics) and the first interaction with microwaves have been observed (Nature). I am working on two antihydrogen experiments, In the ALPHA collaboration we want to test CPT conservation by comparing the 1S-2S energy level difference of antihydrogen with its matter equivalent.

The CPT theorem state that the laws of physics are invariant under invariant under the combined discrete operations of charge conjugation, parity and time reversal. As a consequence, particles and antiparticles must have:

The comparision of the energy difference between the 1S and 2S levels of hydrogen and antihydrogen would be a test of CPT conservation.