In this paper the results of structural changes in ultra high molecular polyethylene (UHMWPE) upon gamma irradiation and storage in nitrogen environment are reported. Based on differential scanning calorimetry (DSC), wide angle x-ray scattering (WAXS), gel content, fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM), we show that upon gamma irradiation crystallinity percentage increases by 20% at high doses due to aging, at low doses up to 50 kGy there is no significant changes. Lamellar thickness increases with the dose, possibly due to chain scission and the addition of new molecular segments to the lamellae. Upon storage in nitrogen DSC data confirmed the appearance of new smaller lamellae. Crosslinking was achieved by irradiation but the ratio of scission to crosslinking is higher after aging. This was confirmed by the increase in the oxidation index and the high brittle behavior of the polymer after aging where fibrous surface was noticed.