The macrolides are still widely used in general practice and the new 14- or 15 membered-ring compounds-roxithromycin, clarithromycin, dirithromycin, azithromycin -may offer a new development. Their antibacterial activity is similar to erythromycin but azithromycin is more active against Gram negative strams. Roxythromycin exhibits high serum concentrations; azithromycin and dirithromycin present low serum concentrations but prolonged half-lives allowing a reduction of the duration of treatment particularly for pharyngitis (azithromycin). Macrolides are less useful for otitis and sinusitis treatment since their activity against H. influenzae and S. pneumoniae are weak. The activity against atypical bacteria justify their choice as first line treatment for benign atypical pneumonia of healthy young adults and for sexually transmitted diseases. In AIDS, these compounds are indicated in mycobacteriosis (clarithromycin), bacillary angiomatosis and excavated pneumonia due to Rhodococcus equi. Clinical tolerance is very good, particularly the gastro-intestinal one. The reported drug interactions are those of this class of antibiotics.