In this article, we examine the contribution of initial skill and slope of progress on alphabetic principle to end of first-grade reading outcomes. Initial skill and slope were measured using DIBELS Nonsense Word Fluency. Reading outcomes were measured at the end of first grade with DIBELS Oral Reading Fluency. Students in Oregon Reading First schools (n = 2,172) and students participating in the DIBELS Data System (n = 358,032), with complete data during the 2004-2005 academic year, were participants. Slope of progress through the first semester of first grade on NWF was a strong predictor of first-grade reading outcomes, especially for students at risk of reading difficulty. (Contains 1 figure and 5 tables.)