The gamma-ray energy spectrum of Blazars in the multi-TeV region places severe constraints on the production mechanism in the source. The highest energy gamma-ray emission in the TeV regime might open the possibility of distinguishing between different scenarios of the gamma-ray production in Blazars (hadronic or leptonic beam). In addition current limits on the infrared extragalactic background can be improved if the energy range of ground-based gamma-ray telescopes can be extended to higher energies (E > 5 TeV). The Whipple Observatory collaboration has detected the two Blazars Markarian 421 and Markarian 501 at an energy threshold of 300 GeV. In order to reach to higher energies the "big flare" from Markarian 421 on May 7 1996 has been used to derive an energy spectrum. The "big flare" data, because of its high gamma-ray flux of 16 gammas/minute, with good statistics can be used to search for gamma-rays in the energy region of 300 GeV - 5 TeV. In addition, a new observation technique, the so-called large-zenith angle technique, has been employed to search for photons with energies of more than 5 TeV from Markarian 421. Due to an increased collection area at large zenith angles, the Whipple 10m imaging atmospheric Cerenkov telescope is more sensitive for energies above 2 TeV than in the normal operation mode at small zenith angles. Both approaches show gamma-ray emission from Markarian 421 with energies of 5 TeV. Implications for AGN models and the nature of the particle beam will be discussed. The current status on the absorption of TeV gamma-rays by the intergalactic IR-background will be related to these data.