During the years 1972-1985, 50 patients with malignant external otitis (MEO) were seen in our department. All our patients complained of severe earache; they presented initially with an apparently simple external otitis, but failed to improve when the usual measures were adopted. They all presented with granulation tissue in the external ear canal, and five of our patients had multiple cranial nerve involvement. MEO is in effect a severe external otitis which, if untreated, proceeds towards an osteomyelitis of the skull base. MEO is more prevalent in the summer, when external otitis is rampant. In some years, a relatively large number of these patients appear; in others there are none. The reason for this is unknown. In Israel, the disease is more prevalent in Jews than in Arabs. Diabetes was present in 68 per cent of our patients-severe diabetes in 42 per cent, mild diabetes in 26 per cent but 32 per cent of our patients were diabetes-free. The only otological past history in our patients was of a recent traumatic insult to the external ear canal; this was the case in about 8 per cent of them. Today, the treatment of choice of this important disease is local debridement supplemented by appropriate antibiotic treatment for 6-8 weeks. This should include some semi-synthetic penicillin to which pseudomonas aeruginosa is sensitive, combined with an appropriate aminoglycoside. During the earlier years of our encounter with MEO, two of our 10 patients died of it; later on, when we learned better how to treat it, the mortality rate decreased.(ABSTRACT TRUNCATED AT 250 WORDS)