Originally published in 1934 in the Cambridge Tracts this volume presents the theory of the distribution of the prime numbers in the series of natural numbers. The major part of the book is devoted to the analytical theory founded on the zeta-function of Riemann. Despite being long out of print, this Tract still remains unsurpassed as an introduction to the field, combining an economy of detail with a clarity of exposition which eases the novice into this area.