Sir William Elderton's Frequency Curves and Correlation was first published in 1906 and subsequently three new editions were published. It has long enjoyed popularity as a source of clear descriptions of the practical use of Pearson and also Gram-Charlie systems of frequency curves. Professor Johnson has substantially revised this book. The material on correlations has been omitted; descriptions of further kinds of frequency curves have been added; the treatment of frequency surfaces has been recast and broadened; and the opportunity has been taken to amend the original text in the light of later research. The aim of this book remains essentially practical. There is no attempt at encyclopaedic coverage of all known systems of frequency curves and surfaces. It should be of especial value as a quick reference book (for statisticians and non-statisticians alike) for formulae and methods used in fitting frequency curves.