This Issue Brief provides a detailed description of the proportion of elementary school students receiving special education in kindergarten, first grade, third grade, and fifth grade; the primary disabilities of these students; and the variation in these measures across a range of demographic and school characteristics. Data for this analysis are drawn from the National Center for Education Statistics (NCES) Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 (ECLS-K). Findings from the analysis indicate that for the cohort of students beginning kindergarten in 1998, specific learning disabilities and speech or language impairments were the most prevalent primary disabilities over the grades studied. The percentage of the student cohort receiving special education grew from 4.1 percent in kindergarten to 11.9 percent of students in fifth grade. The results also indicate that higher percentages of boys than girls and of poor students than nonpoor students received special education. Table 1 presents the percentages of the student cohort receiving special education in the specified grades, by primary disability. Table 2 presents the percentages of students receiving special education in the specified grades by other demographic characteristics (sex, race/ethnicity, and poverty status) and school characteristics (school control, urbanicity, region, and poverty concentration). Table 2 also reports findings separately for students identified as having a learning disability or a speech or language impairment as their primary disability. (Contains 2 tables and 5 endnotes.)