The relationship between particle size and absorption of lead particles from the gastrointestinal tract of the rat has been investigated. Preparations of metallic lead of particle size between 0 and 250 micron were incorporated in laboratory rat diets and absorption determined by measurement of tissue lead concentrations attined under standard conditions. An inverse relationship was found between particle size and lead absorption; this relationship was most marked in the 0 to 100 micron range. A five-fold enhancement of absorption was observed from the diet with lead particles of mean size 6 micron, compared with 197 micron particle size. Lead absorption from dried pain films containing lead chromate and lead octoate was measured using a similar technique. A marked enhancement of absorption was observed for both paints when particle size was reduced from 500 to 1,000 micron to less than 50 micron.