A quartz fallout simulant containing 134Cs was deposited (1.85 g particles/ft2) on 4 common species of grasses used for pasture or turf purposes (Zoysia, Bluegrass, Fescue and Bermuda). Initial interception of the fallout simulant varied between species from 68 to 82% Weathering half lives of particles on foliage average 3.5 ± 0.6 S.E., 36.7 ± 8.6 S.E. and 80.5 ± 39.5 days, respectively, for time periods of 0–2.5, 2.5–35 and 35–48 days following deposition. Particles lost from foliage were mostly trapped by dense mats of stem and dead foliage, and transfer of particles to the soil surface amounted only to 31 % of the original deposition at 48 days. Thus fallout contaminated grasses might be expected to receive greater radiation doses and retain more radioactivity for food chain transfers than other agricultural plants with less effective structures for particle retention.