A series of N',N"-bis(aryl)- and N',N"-(aralkyl)imidodisulfamides was prepared and evaluated as antagonists of slow-reacting substance of anaphylaxis (SRS-A) induced contractions of isolated guinea pig ileum. Some of these compounds, notably N',N"-bis(4-phenylbutyl)-, N',N"-bis[2-(4-chlorophenyl)ethyl]-, and N',N"-bis[2-(4-bromophenyl)ethyl]imidodisulfamides (16, 22, and 26), were moderately potent and selective antagonists of SRS-A. The influence of lipophilic (pi) and electronic (sigma) factors on SRS-A antagonist activity appears to be of considerable importance to the derivation of potent and selective SRS-A antagonists.