MICs and MBCs of four new macrolides (azithromycin, clarithromycin, dirithromycin and roxithromycin) and two older macrolides (erythromycin and josamycin) for Bordetella pertussis and Bordetella parapertussis were determined. The activity of the new macrolides was as good as that of erythromycin, while josamycin was slightly less active. Bordetella parapertussis was more resistant than Bordetella pertussis.