This article reports the outcomes of an experimental evaluation of "Read Well Kindergarten" (RWK), a program that focuses on the development of vocabulary, phonological awareness, alphabetic understanding, and decoding. Kindergarten teachers in 24 elementary schools in New Mexico and Oregon were randomly assigned, by school, to teach RWK or their own program. Treatment teachers received 2 days of training and taught daily lessons. Project staff assessed 1,520 students at pretest and 1,428 at posttest with measures of vocabulary, phonological awareness, alphabetic understanding, and decoding. Follow-up testing was conducted in fall and spring of first grade. Analyses of final outcomes revealed a statistically significant difference favoring intervention students on curriculum-based measures of sight words and decodable words. Although these results did not generalize to standardized measures, follow-up analyses indicated that the impact of RWK rested on the rate of opportunities for independent student practice for letter names, letter sounds, sight words, and oral reading fluency, collected at the end of kindergarten. The findings suggest the potential efficacy of RWK in conjunction with frequent opportunities for independent practice for developing beginning reading skills. (Contains 2 figures and 5 tables.)