Summary: Out of nine strains of Bacillus megaterium from culture collections, only five grew in a minimal medium that contained glucose and ammonium sulphate as principal nutrients. One strain required biotin, while three other strains required two or more amino acids for growth. A freshly isolated strain of B. megaterium required three amino acids for growth. Three strains of Bacillus cereus from a culture collection each required two or more amino acids for growth. From two of these strains, substrains independent of amino acids were developed by serial transfers. Ability to grow in a minimal medium is therefore not so valuable as a distinction between B. megaterium and B. cereus as previously had been supposed.