This paper is concerned with the presence of early Latin linguistic and stylistic elements in a first-century BC text, Lucretius’ De Rerum Natura. The poem notoriously features a variety of optional archaic forms, such as the terminations -ai for the genitive singular of the first declension, and -ier for the passive infinitive. These are found alongside their more standard equivalents -ae and -i, resulting in a mixed style that combines archaisms and non-archaisms. This study offers 1) a full reconsideration of these optional archaisms, providing richer data on their distribution both in the poem and in the hexameter line, and methodological consideration of ‘metrical convenience’, an explanatory concept which is often invoked when dealing with such forms but rarely explored in detail or depth; and 2) a new analysis of features of vocabulary and phraseology that are shared by Lucretius and early Latin authors. A particular concern will be distinguishing, where possible, between the influence of Latin and Greek: Lucretius’ use of compounds is demonstrably influenced by Empedocles, but also by Ennius; his use of tmesis finds some parallels in Homer, and some in Early Latin.