The existence of small particles emitted from the dehiscing anther at the time of pollen shedding is shown. We examined pollen samples of five plants causing pollinosis in Japan:Cryptomeria japonica, Alnus japonica, Quercus serrata, Dactylis glomerataandAmbrosia elatior. The pollen samples ofC. japonicacollected by hydroponic culture had two kinds of particles. The size of these particles was 0.46 to 1.4 μm and 29 to 40 μm (pollen grains) in diameter. The number of the small particles was about 8-fold greater than that of intact pollen grains.Alnus japonica, Quercus serrataandDactylis glomerataalso discharge small particles other than pollen grains although the number is not so large asCryptomeria japonica. We could not recognize any small particles in a pollen sample ofAmbrosia elatior.