A standardized protocol for a pediatric heel-rise test was developed and reliability and validity are reported. Fifty-seven children developing typically (CDT) and 34 children with plantar flexion weakness performed three tests: unilateral heel rise, vertical jump, and force measurement using handheld dynamometry. Intraclass correlation coefficients (ICC) varied from 0.85-0.99 for reliability analyses in both participant groups. Construct validity analysis revealed a significant difference between groups (F = 44.57, p less than 0.05) and age-related differences among CDT; 5- to 8-year olds (mean = 15.2, SD = 5.4) performed fewer repetitions compared to 9- to 12-year olds (mean = 27.7, SD = 11.7) (p less than 0.05). Age explained 41% of the variance in the number of heel-rise repetitions. Correlations between the three tests (r = 0.56 to 0.66) provide evidence of convergent validity. The results indicate that the standardized protocol is both reliable and valid for use in 5- to 12-year-old children with and without plantar flexion weakness. (Contains 4 tables and 3 figures.)