The settling velocity in still air of natural and dyed spores and pollen of several species was measured using the method of McCubbin and was found to be as follows (in cm s-1): black spruce (Picea mariana), 3.19; jack pine (Pinus banksiana), 2.53;Lycopodium, 2.31; dyedLycopodium, 2.15; oil palm (Elaeis guineensis), 3.00; dyed oil palm, 2.16 and corn(Zea Mays), 30.95. The percentage of clustered spores and pollen was taken into account but was not found to significantly affect settling velocity except in the case of dyed oil palm. Comparisons of the measured settling velocities of clustred grains were made with the model of Ferrandino and Aylor. This was found to be accurate in general, but tended to over-estimate the settling velocity of clumped spores ofLycopodiumand of dyed pollen of oil palm.