The Influence on the hearing and the vestibular function of 37 pilot of a Jet plane T-33A before and after flying was studied and the following results have been obtained. The air conduction audiogram showed the loss of the hearing 32.1% of the pilots and the degree of the loss was 10db in 2/3 and from 15 to 20 db in approximately 1/3 of them, and the frequency and degree of disturbance were more significant in the higher tone range above 4, 000 cps, especially in 6, 000cps.The change in the bone conduction was observed in 38.3% of the pilots, but it was smaller in comparison with the air conduction.In the lowea tone range below 500cps, the hearing showed a slight increase and in above 1000cps a small degree of loss was obs erved.The number of flying experience did not indicate any difference in the incidence of the disturbance, but in all he pilots including those received no influence, the change in the hearing was minimal in the group having more number of years of flying experience in the lower freq- uencies below 1, 000cps and inversely their db loss was greater in above 2, 000cps. The vestibular function was examied before and after flying Romberg's sign was more mor- ked in 83.3% of these cases after flyiug and the inversion angle decreased by Goniometry in 73.0 % and the average value of postrotary Nystagmus showed 2.6 times increase after flying.The percentage and degree of disturbance was found less among those having longer years of flying experience, suggesting some adaptability to the stimuli.