Pollinosis is a term used to designate hay fever or asthma caused by contact with pollens to which the patient is allergic. It is known as a common disease in the United States and European countries but not yet well documented in Korea, the question still being open if this is due to a low frequency or lack of investigations in this country. Air borne pollen counts have so far not been reported in Korea, therefore the author has made a study of airborne grains collected inside a hospital compound in the center of Seoul during the period 1962 to 1964. The equipment used was a shelter containing a slide wetted with Phöbus-Blackley solution tinted with gentiana violet. Four times weekly slides were exposed during 24 hours. The shelters were placed on two levels, one at the height of two meters and the other at ten meters. Humidity must be considered, since the movability of the pollen grains is favored by low humidity. When strong winds are prevailing pollen grains can be obtained several hundred miles from their source. This was most obvious during May. Thirteen kinds of pollen were found during the three years. The pollination period for trees ranged from April to May, Carpinus Tschonoshii and Pine being prevalent. Marked peaks of Pine were found in May. Pollination of grasses began in March and continued till October. Graminaceae and Capsella Bursa-Pastoris were prevalent. The weed season ranged from August to October. The Humulus Japonica and Chrysanthemum were prevalent, ragweed was however not found.