Techniques are described for the production of heavy concentrations of aquatic Hyphomycete spores, for estimating the spore concentration, the sedimentation rate of spores and their trapping efficiency on smooth cylinders. No correlation could be discovered between the rates of sedimentation and spore shape. Trapping experiments showed that the trapping efficiency of the tetraradiate spores was higher than that of spores of different shape. It is suggested that the higher efficiency might be the result of contact of the tetraradiate spore at three points on a surface.