This article is an account of research on propolis and poplar bud exudate at the Department of Plant Sciences, Oxford. It is not a general review of propolis research: such reviews are available elsewhere. Some of the results reported here have already been published but others are novel. Propolis is the material used by bees as a glue and general purpose sealer and draught excluder for beehives. It consists primarily of plant exudates gathered by bees and mixed with beeswax which they secrete, together with small amounts of sugar. The constituents of beeswax have already been reported in detail and we here consider only the plant exudate fraction of propolis. This is usually separated from the wax by extraction into 70% (by volume) alcohol, and is termed propolis balsam.