Bioaerosols of interest in plant pathology are comprised principally of the air-borne or splash-borne fungal spores or bacterial cells which disperse many plant diseases. Plant pathogen inoculum is mostly sampled out of doors, imposing environmental constraints on sampling methods arising for the need to sample in fluctuating winds and to protect samples from rain. The choice or method of sampling can be affected by biological considerations, such as when and where inoculum is released and the size and shape of the propagules. These considerations are discussed in relation to choice of sampling methods for use in plant pathology studies. Passive deposition samplers, bait plants and volumetric samplers (suction and rotating-arm) are described and their advantages and disadvantages are discussed. Current samplers rely almost exclusively on optical microscopy or culture methods for identifying and enumerating air-borne plant patho en inoculum. Recently, developed immunological techniques for the detection of air-borne plant pathogens are briefly considered.