EGRET gamma-ray blazars: luminosity function and contribution to the extragalactic gamma-ray background

We describe the properties of the blazars detected by EGRET and summarize the results on the calculations of the evolution and luminosty function of these sources. Of the large number of possible origins of extragalactic diffuse γ-ray emission, it has been postulated that active galaxies might be one of the most likely candidates. However, some of our recent analysis indicate that only 25% of the diffuse extragalactic emission measured by SAS-2 and EGRET can be attributed to unresolved γ-ray blazars. Therefore, other sources of diffuse extragalactic γ-ray emission must exist. We present a summary of these results in this article.