A new Ni-Cr-Mo corrosion resistant alloy, Hastelloy alloy C-4, has been developed that does not precipitate an intermetallic Mu phase upon aging in the 650 to 1090 C temperature range. This further improvement of Hastelloy alloy C-276 has evolved from a detailed study of the effects of the substitutional and interstitial elements on the precipitation of intermetallic and carbide phases. Data have been generated to show that Hastelloy alloy C-4 is basically equivalent in corrosion resistance to its predecessors in both oxidizing and reducing media.