Lucretius' Epicurean account of dreams in Book IV of De Rerum Natura indicates that they are wholly void of prophetic significance and of little practical significance. Dreams, rightly apprehended, do little more than mirror our daily preoccupations. For Lucretius, all dreams pass through the gate of ivory and all are reducible to psychophysical phenomena.In this paper, I examine Lucretius' account of sleep and the formation of dreams in light of the Epicurean aims of the poem as a whole. In doing so, I give what I take to be a plausible sketch of the formation of dreams through what I call Lucretius' "selection model" of dreams. The selection model forbids, strictly speaking, the phenomenon of genuine prophecy through dreams, while at the same time it allows for a surprisingly rich psychophysical explanation of the genesis of seemingly prophetic dreams in sleepers. Thus, I argue, a proper grasp of the Lucretian account of oneiric formation is itself a significant part of the Epicurean cure for superstitions and religiously based ills of his day.