The author reasserts his original definition of palynology as the study of plant spores and their dispersal and applications thereof, and here considers aeropalynology as that branch of palynology which is concerned with the dissemination of plant spores in both theory and practice. During the present century important advances in methods of sampling atmospheric spores have been made and have been applied at a limited number of locations in England, Wales and Scotland either with a view to assessing the general (outdoor) aerospora of the region concerned or of various special habitats. Variation both ‘circadian’and annual in the incidence of various spore types has been studied. The atmospheric transport of microbes (dispersal in the wider sense) which embraces take-off (liberation), free flight (dispersion proper) and landing (deposition) has occupied the attention of several workers. Advances have been made also in intramural palynology. The fact that the aerospora is a reflex of the vegetation has been recognized but not worked out in detail despite the abundant data available. Finally the author claims that the many applications of aeropalynology both potential and actual, would amply justify further long-term observation and assessment of the aerospora.