One of the common sites of infection in leukemic patients is paranasal sinus(PNS). The aims of this paper were(1) to evaluate the incidence of PNS infection and (2) to emphasize the need of routine check of PNS roentgenograms in leukemic patients. We analyzed PNS roentgenograms of 177 pathologically proven leukemic patients during the period from January 1980 through December 1986, and following results were obtained. (1)One-hundred-five were men and 72 were women with the age ranging from 2 to 72 years(mean age being 33.2 years).(2) The number of patients with PNS infection was 82 or 46.3%. The incidence was three times higher than that of general population(16%). (3) The age incidence was 85.7% in the 1st decade, 73.9% in the 4th decade, and 36% in 2nd decades in decreasing order. (4) The maxillary sinus was involved in 86.6% and ethmoid sinus in 23.2%.Retention cyst was noted in maxillary sinus in 13.4%.