Purpose: The extant literature suggests that exposure to novel vocabulary words through repeated readings of storybooks influences children's word learning, and that adult elaboration of words in context can accelerate vocabulary growth. This study examined the influence of small-group storybook reading sessions on the acquisition of vocabulary words for at-risk kindergartners, and the impact of word elaboration on learning. An additional goal was to study differential responses to treatment for children with high versus low vocabulary skill. Method: Using a pretest-posttest comparison group research design, 57 kindergartners were randomly assigned to a treatment (n=29) or comparison (n=28) group. Children were also differentiated into high (n=31) versus low (n=26) vocabulary skill groups using scores on a standardized receptive vocabulary test. Children in the treatment group completed 20 small-group storybook reading sessions during which they were exposed to 60 novel words randomly assigned to non-elaborated and elaborated conditions. Pre- and posttest examined the quality of children's definitions for the 60 novel words. Results: Overall, word-learning gains were modest. Children in the treatment group made significantly greater gains in elaborated words relative to children in the comparison group; no influence of storybook reading exposure was seen for non-elaborated words. Children with low vocabulary scores made the greatest gains on elaborated words. Clinical Implications: Suggestions are offered for using storybooks as a clinical tool for fostering vocabulary development. As an efficacy study, results should inform future applied research on word learning for at-risk children.