Analysis of data from the EGRET γ-ray detector on the Compton Gamma Ray Observatory indicated an anomaly in the form of an excess diffuse galactic flux at GeV energies over that which was theoretically predicted. Various explanations for this anomaly have been put forth, including the invocation of supersymmetric dark matter annihilation. We reexamine these explanations here, including a new discussion of the possible systematic errors in the sensitivity determination of the EGRET detector. We conclude that the most likely explanation of the EGRET “GeV anomaly” was an error in the estimation of the EGRET sensitivity at energies above ∼1 GeV. We give reasons why such a situation could have occured. We find evidence from our new all-sky analysis which is inconsistent with the assumption that the anomaly can be a signal of supersymmetric dark matter annihilation. We also reconfirm the original results of the EGRET team on the extragalactic γ-ray background spectrum. There are important implications of our analysis for the upcoming gamma ray large area telescope (GLAST) mission.Keywordsγ-raysBackground radiationReferencesF.W.SteckerAstrophys. J.212197760S.D.HunterAstrophys. J.4811997205A.K.HardingF.W.SteckerNature2901981316M.PohlJ.A.EspositoAstrophys. J.5071998327A.W.StrongI.V.MoskalenkoO.ReimerAstrophys. J.6132004962W.De BoerAstron. Astrophys.444200551A.W.StrongI.V.MoskalenkoO.ReimerAstrophys. J.6132004956P.SreekumarAstrophys. J.4941998523F.W.SteckerAstrophys. Space Sci.61970377F.W.SteckerCosmic Gamma Rays1971Mono Pub.BaltimoreF.W.SteckerAstrophys. J.1851973499Y. Shikaze et al., e-print <astr-ph/0611388>.V. de Ataíde Malafaia Lopos dos Santos, e-print <astro-ph/nucl-th/0602026>.C.D.DermerAstron. Astrophys.1571986223F.W.SteckerM.M.ShapiroJ.P.WefelCosmic Gamma Rays, Neutrinos, and Related Astrophysicsvol. 451989KluwerDordrechtF.W.SteckerAstrophys. J.2281979919T.KamaeAstrophys. J.6472006692M.MoriAstrophys. J.4781997225P.GralewiczJ.WdowczykA.W.WolfendaleL.ZhangAstron. Astrophys.3181997925In Ref. the approach is taken of arbitrarily raising the cosmic-ray proton and electron spectra by different amounts in order to optimize the fit to the reported EGRET GeV anomaly. We see no basis for these ad hoc assumptions, particularly as the proton flux is well measured .