Acute mastoiditis is now an uncommon finding. The early use of the various antibiotics has made surgical mastoiditis a rarity. A comparatively new pathogen 'Pseudomonas maltophilia' was the causative organism in this case. Pseudomonas maltophilia responds only to Garamycin and Polymixin B. Unless one of these two antibiotics is used in its treatment, it will continue to cause a severe infection.