Apart from the coverage given to it in the grammars, number in English nouns has received relatively little attention, especially in the area of theoretical considerations. Guided by the principles of psychomechanics, Hirtle (1982a) put forth a fairly elaborate theory of number in English nouns. The aim of this work is to provide evidence to validate parts of Hirtle's theory, to verify some of his analyses, and to investigate several problems, some of which are mentioned in his work as subjects for further research. Specific areas treated are ailment nouns, liquid names, ending in -ings, binary objects, abstract -s, and external singulars.