The gamma-ray telescopes on the Compton Gamma Ray Observatory (CGRO) have so far observed gamma-ray emission above an energy of 1 MeV from 7, possibly 8 pulsars: 6 (7) radio pulsars and the radio dim pulsar Geminga. Detections at optical and X-ray energies are also available for most of these pulsars, proving that these objects emit a wide spectrum of high energy radiation. The peak luminosities in the multiwavelength spectra of these pulsars is found to range above hard X-rays extending up to several GeV. The efficiency to convert rotational energy into high-energy radiation increases systematically with age of these pulsars and the observed gamma-ray spectra in the EGRET energy range become correspondingly harder. For several of the the brighter pulsars, phase resolved spectra have been derived showing significant spectral changes over the pulsar's rotation.
The detected gamma-ray light curves show mostly two peaked emission patterns; only PSR B1706-44 and PSR B1509-58 have more complex light curves. At lower energies the light curves appear quite unrelated to the gamma rays in all cases except the Crab pulsar, which indicates the complexity of the magnetospheric emission processes in young pulsars.
The main competing models, 'polar cap' and 'outer gap' scenarios, have achieved to explain many individual features of high-energy pulsars but no comprehensive, self consistent treatment of particles, fields, and radiation is yet available. Progress in understanding the emission processes is critical for questions related to the detection and population statistics of more high-energy pulsars, and the total contribution of high-energy pulsars to the galactic gamma-ray emission. We expect that the new and planned high-energy missions (Chandra, XMM, Astro-E, GLAST) will contribute significantly to the multiwavelength studies of pulsars.