Single biotin doses (600 micrograms and 900 micrograms) orally administered to male and female volunteers were very rapidly eliminated from plasma after absorption leading to a remarkable increase of urinary excretion. A prolonged enhancement of plasma levels occurred only after continuous supplementation with 300 micrograms biotin/day for 1 week and following 900 micrograms biotin/day for another week. From the diurnal turnover of the plasma level after oral stimulation with 600 micrograms biotin some biokinetic indices, such as the constants of invasion and elimination rate as well as the elimination half life time were determined. The median of the invasion constant was calculated to 2.068 h-1, that one of elimination constant to 0.3867 h-1 suggesting no indication of diminished body stores. The elimination half life time of the administered biotin dose from plasma amounted to 1 hour, 50 minutes.