SummaryFreshly dehisced pollens from four common grasses were each divided into two portions. One portion of each was placed in an extracting fluid within 2 hr of being shed (viable pollen) and the other portion was kept at room temperature in a desiccator for 2 weeks (non‐viable pollen) before extraction. The relative skin test activity of each pair of extracts was determined on grass pollen sensitive patients.No significant difference was detected between the extracts of the viable and non‐viable pollens in any of the four species exami