Nineteen 2-halogeno-acetamides, -propanamides, and -iso-butyramides and four related epoxyamides were tested as mutagens for Salmonella typhimurium TA100. Mutagenic activity was observed in strictly selected 2-halogenoamides and in all epoxyamides. The effectiveness of 2-halogenoamides depends upon: the character of the carbon carrying the halogen (1 degree, 2 degrees, 3 degrees); the nature of the halogen (Br, Cl); the substitution at nitrogen. Some considerations concerning the selectivity observed are presented.