In 1986, the New York City Public Schools adopted a cohort methodology for determining dropout and graduation rates. The Class of 1990 was the primary cohort studied in this report; it was the fifth cohort to be studied for at least 4 years using this methodology. Follow-ups are reported for three preceding classes. The 1990 cohort, who entered high school in 1986, contained 78,936 students. Their status was determined as of June 30, 1990, their graduation date, with each student having one of four possible outcomes at the end of four years: (1) graduation; (2) dropout; (3) discharged from the system; and (4) still enrolled. The same methods were used for follow-up studies of the classes of 1987, 1988, and 1989. The dropout rate in 1990 (19.2%) was the lowest of the five cohorts studied to date. The graduation rate (37.6%) showed a small decline (0.4%) below the 1989 figure. Concomitant with these figures was an increase of 2.4% in the number of students enrolled for a fifth year of high school, probably attributable to at-risk students who continued in school. If the slight downward trend in the dropout rate continues, meaningful decreases could occur as the holding power of schools gradually increases. Specific information is given for the status and academic achievement of the 1990 cohort; the status of the follow-up cohorts; preliminary expectations for the classes of 1991 and 1992; and comparisons across cohorts, with attention to the racial and ethnic backgrounds of the cohorts, students in special education, and dropout rates. Statistical data are presented in 33 tables and four graphs. Seven appendices provide supplemental information. (SLD)