Analysis of a large number of fossil pollen grains of Tilia from the East Anglian Fenland, led to examination of the characters that might be employed to separate T. platyphyllos from T. cordata. Certain characters were discarded but mesh structure and size in surface reticulation, characters since accepted by other authors, were regarded as satisfactory and made the basis for classifying fossil grains. The results indicated native British status for both species of lime from pollen-zone Vila onwards, with T. cordata much the commoner, and very high relative frequencies of Tilia pollen in zone Vila and diminution zone by zone thereafter to levels below 0.5% of total tree pollen.