In criticizing studies of fossil pollen extracted from rock samples, positive results have been questioned or even discredited with the claim that various grains on the slides are merely the result of atmospheric, non-fossil pollen which contaminated the sample in the field or laboratory. Here we have undertaken to assess the rate at which pollen grains will actually contaminate exposed slides-with the goal of determining just how valid are the claims that pollen contamination might routinely occur in the laboratory or during field work.