A bstract. Asteroids, meteorites and fireballs with visual magnitude M < -5 are shown to have the same mass dis- tribution. Bright fireballs are therefore asteroidal debris, whereas the fainter meteors originate in the nuclei of comets. The influx of cometary meteors equals the influx of asteroidal meteors at a visual magnitude of -3. The percentage of asteroidal meteors varies from 90 per cent at magnitude = -10 to 7 per cent at magnitude = +5. A fireball of mag- nitude - 10 travelling with a velocity of 17 km has a mass of 40 kg on entering the earth's atmosphere and produces a meteorite weighing approximately 10 kg. The earth on the average encounters 3.3 fireballs per day with magnitude -10 and collects an asteroidal fragment with mass > 4,000 tons every hundred years.