Clinical examinations were performed in 1969 on patients with allergic occupational asthma caused by inhaling the body fluid of sea-squirts attaching to the shell of cultured oyster. The allergic symptoms caused by inhaling the body fluid of sea-squirts were rhinitis, conjunctivitis, bronchitis and bronchial asthma. The sea-squirt asthma was observed in 43 out of 201 oyster shuckers. Positive skin test was seen in 95.2% of 21 cases with sea-squirt asthma. And Prausnitz-Kustner reaction of the asthma was observed in 10 out of 11 cases. Obstrutive disturbance in lung function tests was shown only in a few cases because examination was performed in resting intervals and the subjects were of old age. It is clear that there is a close relation between basophils and allergic reaction caused by sea-squirt asthma as shown by an increase of basophils in the pre-attack stage of working periods.