A research team consisting of educators of gifted students, a scientist, and experts in measurement developed a performance-based assessment of life science skills and abilities. Four high schools in the Southwestern United States were the settings for field testing and implementation. Five levels of ratings were given: "unknown," "maybe," "probably," "definitely," and "wow." The majority of student scores were in the maybe and probably categories. Using six new measures (concept maps in life and physical science, math problem solving, spatial analytical performance assessment, life science performance assessment and physical science performance assessment), 23 students (M2) were selected for participation in science laboratories at an R1 university along with 20 students (M1) selected by conventional means. When the nine attribute scores of the performance-based assessment were compared, no significant difference was found t(41), p > 0.38, between M1 and M2 students. Performance-based assessments in science, technology, engineering, and mathematics (STEM) will provide an alternative and a complement to standard achievement tests. They have the potential to identify and nurture exceptionally talented high school students across all demographic groups.