The competitive characteristics of motor sports were clarified by determining physical strength in a variety, cardiac function during a race, loads (acceleration and noise) suffered by drivers during a race, etc. , and these results were published in the previous reports (Des-cente Sport Science, 1990). In the present study, the loads suffered by drivers during a race were examined from a viewpoint of blood biochemistry. The subjects are 14 racing drivers in F-3, F-3000, Group C, etc. The test items of hematology are cortisol, the renin-angiotensin-aldosterone system, adrenaline, noradrenaline, other various hormones, enzymes, electrolytes, etc.
　As a result, blood cortisol concentrations, which are ususally very stable, showed very high values after a race. Particularly, in cases with a high speed and a long racing time, a tendency showing a high value was observed. On the other hand, ACTH values showed cha-nges within normal ranges even after a race. The renin-angiotensin-aldosterone system showed a very high value in any case after a race. Also, evaluations in blood concentrations of lactic acid, FFA, myoglobin, etc. were observed. Other blood biochemical findings showed electrolytes, hepatic function, renal function, etc. all in normal ranges.
　From the above results, the competitive characteristics of motor sports are raised as follows :
　1. Physic stress seemed to belong to the maximum degree in view of the increase in heart rate and the elevations in blood con-centrations of cortisol, the renin-angiotensin system, adrenaline, noradrenaline, etc.
　2. Motor quantity seems to be moderate or slightly high.
　3. The higher the class, the greater the load suffered by a live body. Also, it can be said that the faster the speed in a race or the longer the racing time, the greater the stress.

DESCENTE SPORTS SCIENCE Vol.12/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE