Characteristics of 292 youths (269 males and 23 females) identified by high scores (before the age of 13) on the Scholastic Aptitude Test-Mathematics as part of the Study of Mathematically Precocious Youth (SMPY) at Johns Hopkins University are reported. Several of the students have received Ph.D. degrees at very young ages. The young students also scored substantially higher on the verbal section of the SAT and the Test of Standard Written English than did average college bound high school seniors. More variability was found among male high scorers. Two students were Black, 22% were of Asian parentage. Parents of the group were well educated averaging a master's degree for fathers and a bachelor's degree for mothers. Paternal occupational status was consistent with educational level. Seventy percent of the girls and 63 percent of the boys were the oldest in their families, with 17 percent of the girls and 11 percent of the boys being only children. Most of the students had accelerated grade placement by the end of high school and college. An appendix describes procedures for participating in the ongoing talent search. (DB)