Abstract: Pettersen, SA and Mathisen, GE. Effect of short burst activities on sprint and agility performance in 11- to 12-year-old boys. J Strength Cond Res 26(4): 1033–1038, 2012—There are limited data on how coordinative sprint drills and maximal short burst activities affects children's sprint and agility performance. The purpose of the present study was to investigate the effect of short burst activities on sprint and agility performance in 11- to 12-year-old boys. A training group (TG) of 14 boys followed a 6-week, 1-hour·week−1, training program consisting of different short burst competitive sprinting activities. Eleven boys of similar age served as controls (control group [CG]). Pre- and posttests assessed 10-m sprint, 20-m sprint, and agility performance. Results revealed significant performance improvement in all tests within TG (p < 0.05), but not between TG and CG in the 10-m sprint test. Furthermore, the relationships between the performances in straight-line sprint and agility showed a significant transfer effect (r = 0.68–0.75, p < 0.001). Findings from the present study indicate that competitive short burst activities executed with maximal effort may produce improvement in sprint and agility performance in 11- to 12-year-old boys.