There are many published reports on the anti-inflammatory effects of macrolides, some dating back to the introduction of erythromycin. Macrolides have been shown to affect a number of the processes involved in inflammation, including the migration of neutrophils, the oxidative burst in phagocytes and the production of various cytokines, although the precise mechanisms are not clear. These effects have been linked to the ability of macrolides to accumulate in mammalian cells. Roxithromycin, a macrolide with better plasma concentrations and higher tissue concentrations than erythromycin, has been tested in a standard animal model used for evaluating anti-inflammatory drugs. When rats were given a prophylactic dose (20 mg/kg), roxithromycin suppressed the oedema produced by injecting carrageenin into the paw with effects almost equal to that seen with the non-steroidal anti-inflammatory drug nimesulide. Azithromycin and clarithromycin, macrolides with better pharmacokinetics than erythromycin, only showed slight anti-inflammatory effects. These results confirm that roxithromycin has anti-inflammatory properties in vivo and encourage the investigation of its mode of action.