~~The present study was to investigate the functional changes of kidney and some electrolytes in professional football players before, and after competition. Fourteen football players participated in this competition for 90 minutes with 15 minutes rest between sections (full time). Before-competition, 30 minutes after-and 24 hours after competition, blood and urine were collected and determined BUN, creatinine and other electrolytes including sodium, potassium chloride and bicarbonate. The results showed that creatinine, a renal function marker was significant increased after competition and declined back to pre-competition level again during 24 hours recovery period. For electrolyte, chloride was increased but bicarbonate was significantly decreased after 24 hours recovery time when compare to pre-competition. From this study, it can be concluded that after full time football competition, creatinine was dramatically increased and some electrolytes including chloride and bicarbonate were changed. However, these values did not exceed normal range. Therefore it was implied that the training in Thai football sport is relatively safe in terms of renal function, the athlete remain healthy even after competition.