Tetracycline and its congeners demonstrate antimicrobial activity against bacteria, Chlamydiae and Toxoplasma gondii. Ophthalmologists can use these drugs to treat bacterial and chlamydial infections, and also for ocular rosacea and similar disorders. Side effects associated with systemic tetracycline use are most commonly related to the gastrointestinal tract and to signs of yeast superinfection. Minocycline use may be limited by its vestibular toxicity. Temporary growth retardation and staining of erupting teeth may occur with oral use of tetracycline in children under 8 years; these drugs should not be given in pregnancy or to young children. Topical tetracycline application yields good tear and aqueous humor concentrations.