The new macrolides, notably clarithromycin and azithromycin, are significant advances over previous agents. With an extended antibacterial spectrum, increased activity, improved absorption and excellent tissue and intracellular penetration, they realize therapeutic aims which have been increasingly sought in the 1980s. They are likely to find an extended role in respiratory tract infections, especially in community-acquired pneumonia, where the activity against β-lactam-resistant bacteria and intracellular pathogens, e.g. Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae have a significant role to play. Realistic twice or once daily dosing will prove a powerful argument for their use and the major improvement in gastrointestinal tolerance compared with erythromycin is likely to prove a deciding factor in their favour. © 1991.