Research Findings: Children learn most of their vocabulary incidentally, by hearing words used in their environment. This study explored which kinds of presentations of words, without any direct instruction, yielded greater depth of target word knowledge. Changes in 56 kindergartners' depth of knowledge for each of 23 novel target words (N = 1,288) based on presentation in 1 of 3 conditions (read-aloud, teacher conversation, or both read-aloud and conversation) were explored and compared to control words that were never presented. A 2-level, cross-classification analysis modeled the postintervention score for each word for each child. Children's word meaning knowledge improved most when words were presented via combined conversations and read-alouds. Vocabulary gains for words presented via conversations differed across classrooms. Practice or Policy: Both teacher conversations and read-aloud presentations of target vocabulary should be used together. Professional development for teachers' effective vocabulary conversations may be needed.