Stress corrosion cracking (SCC) of the high performance rare-earth containing magnesium alloy Electron 21 was studied using slow strain rate test (SSRT). Glycerol distilled water and 0.01N and 0.1N NaCl solutions saturated with Mg (OH)2 were employed. For comparison a well-known AZ91E alloy was also studied. SSRT studies indicate that both the alloys were susceptible to SCC to some extent in 0.1N 0.01N NaCl solutions and distilled water. However Elektron 21 had higher SCC resistance than AZ91E. The fractography of SSRT tested AZ91E and Elektron 21 specimens were largely found to be transgranular (TGSCC) in distilled water. However in 0.1N and 0.01N NaCl solutions AZ91E exhibited transgranular while Elektron 21 showed predominantly intergranular (IGSCC) fracture.