Treatment of infections caused by microorganisms susceptible to doxycycline, particularly respiratory (pneumonia, bronchopneumonia, kennel cough, feline respiratory disease, pharyngitis, tracheitis, bronchitis and sinusitis), dermatological (otitis, abscesses and cellulitis), joint, genitourinary, intestinal (gastroenteritis), leptospirosis, anaplasmosis, ehrlichiosis and brucellosis.