Objective Changes in cerebral N-acetylaspartate and choline (NAA/Cho) or creatine (NAA/Cr) following a mild traumatic brain injury (mTBI) in sport have been measured by 1H (Proton) magnetic resonance spectroscopy (1H-MRS). We intend to investigate the effect that presenting symptomatology has on these parameters. Design Observational cohort study. Setting UK Premiership and Championship Rugby. Participants Athletes aged 18-40 years. Interventions (or assessment of risk factors) Concussed athletes identified by members of their enhanced-care clinical team. Imaging undertaken on a Philips Achieva 3.0 T MR scanner (32 channel SENSE coil). A PRESS sequence (et 37 ms, rt 2000 ms) generated spectra in a 20 mm MRS cubic voxel in right-sided superior frontal white matter. Symptoms were assessed using the IMPACT and SCAT-3 concussion assessment tools. Recruits were divided into either ‘symptomatic’ or ‘non-symptomatic’ at presentation based on a minimum severity score from either of these assessments. Outcome measures Analysis of raw parameters was undertaken utilising the TARQUIN 1H-MRS analytical software package. A Mann-Whitney-U test was performed to compare results between the symptomatic and non-symptomatic groups. Main results 33 concussed professional athletes were recruited. Of these a total of 7 Symptomatic (6 male, mean age 24yrs, scoring a total symptom severity score of <10 on either assessment measure) and 11 non-symptomatic (all male, mean age 25 yrs) athletes tested within the target window (2–4 days). Ratios between groups did not vary significantly (NAA/Cho mean 4.43 vs 4.53 and NAA/Cr 1.24 vs 1.26, p=0.84 and p=0.99 respectively). Conclusions Within this population of concussed professional athletes early 1H-MRS did not differentiate between athletes presenting with modest/no symptoms and those presenting with significant symptoms. Competing interests None.