Retrospective studies are important in ALS but require markers of disease severity to enable risk adjustment and to allow fair comparisons between patient groups. The ALSFRS-R could be used as such a measure. This study aimed to determine if accurate ALSFRS-R scores could be generated by reviewing clinic notes. Five investigators reviewed 100 de-identified clinic notes to generate estimated ALSFRS-R scores. These scores were compared to ALSFRS-R scores completed by patients within three months of the clinic note. The retrospective ALSFRS-R scores did not differ significantly from the actual scores (mean retrospective score 38.7+/-5 vs. actual score 38.4+/-6, p =0.5). The intra-class correlation coefficient between actual and retrospective scores confirmed reasonable agreement (rho = 0.53, p <0.001). Bland Altman analysis also confirmed good agreement between the actual and retrospective scores. This study indicates that ALSFRS-R scores can be accurately reproduced from information in clinic notes and should be considered as a marker of disease severity for use in retrospective studies.