The synthesis of new [(dialkylamino)alkyl]pyridylacetamides is reported. These compounds displayed a potent antiarrhythmic activity, as demonstrated on a model of myocardial infarction in the conscious dog. Structure-activity relationships are discussed within a series of 22 homologues, comparing relative antiarrhythmic properties and cardiac side effects. One of these compounds, 15, has been selected as a candidate for clinical evaluation in man.