For a work written more than two thousand years ago, in a society in many ways quite alien to our own, Lucretius' De Rerum Natura contains much of striking, even startling, contemporary relevance. This is true, above all, of the fifth book, which begins by putting a strong case against what it has recently become fashionable to call 'intelligent design', and ends with an account of human evolution and the development of society in which the limitations of technological progress form a strong and occasionally explicit subtext. Along the way, the poet touches on many themes which may strike a chord with the twenty-first century reader: the fragility of our ecosystem, the corruption of political life, the futility of consumerism and the desirability of limiting our acquisitive instincts are all highly topical issues for us, as for the poem's original audience. Book V also offers a fascinating introduction to the world-view of the upper-class Roman of the first century BC. This edition (which complements existing Aris and Phillips commentaries on books 3, 4 and 6) will help to make Lucretius' urgent and impassioned argument, and something of his remarkable poetic style, accessible to a wider audience, including those with little or no knowledge of Latin. Both the translation and commentary aim to explain the scientific argument of the book as clearly as possible; and to convey at least some impression of the poetic texture of Lucretius' Latin.