UNLABELLED: The King-Devick (KD) oculomotor test has recently been advocated for sideline diagnosis of concussion. Although visual processing and performance are often impaired in concussion patients, the utility of KD as a concussion diagnostic tool is not validated. PURPOSE: To examine the diagnostic value of KD, by comparing KD with post-concussion symptom scale (PCSS) and ImPACT(R) composite scores. We hypothesized that KD would be correlated with visual motor speed/memory (VMS, VIS) and reaction time (RT), because all require cognitive visual processing. We also expected parallel changes in KD and PCSS across recovery. METHODS: Thirty-five concussed individuals (12-19 y; 18 females, 17 males) were evaluated with PCSS, ImPACT(R) composite and KD scores over four clinical visits (V). RESULTS: KD times improved with each visit (DeltaV1-V2: 7.86+/-11.82; DeltaV2-V3: 9.17 +/- 11.07; DeltaV3-V4: 5.30 +/- 7.87 s) and paralleled improvements in PCSS (DeltaV1-V2: 8.97 +/- 20.27; DeltaV2-V3: 8.69 +/- 14.70; DeltaV3-V4: 6.31 +/- 7.71), RT (DeltaV1-V2: 0.05 +/- 0.21; DeltaV2-V3: 0.09 +/- 0.19; DeltaV3-V4 0.03 +/- 0.07) and VMS (DeltaV1-V2: -5.27 +/- 6.98; DeltaV2-V3: -2.61 +/- 6.48; DeltaV3-V4: -2.35 +/- 5.22). Longer KD times were associated with slower RT (r = 0.67; P<0.0001) and lower VMS (r = -0.70; P<0.0001), respectively. CONCLUSION: Cognitive visual performance testing using KD has utility in concussion evaluation. Validation would further establish KD as an effective ancillary tool in longitudinal concussion management and research.