The process of performance appraisal can serve important employee development as well as organizational administrative functions. However, the reliable and accurate assessment of performance could be hampered by rating errors such as halo, leniency, and central tendency. Because the traditional approach to appraisal by means of graphic rating scales is considered to be susceptible to these errors, behaviourally based measures have been developed which have the claimed advantage of being relatively resistant to rating errors. This study compared the ratings given to a group of employees on a graphic rating scale and a behavioural observation scale. The results did not support the superiority of the BOS in resisting rating errors. Opsomming Die proses van prestasiebeoordeling speel 'n belangrike rol in die ontwikkeling van werknemers asook om administratiewe besluite te maak oor personeel. Die betroubare en akkurate evaluering van werkprestasie kan egter belemmer word deur beoordelingsfoute soos die stralekranseffek, toegeeflikheid, en sentrale neiging. Omrede die alombekende grafiese beoordelingskaal veronderstel is om baie vatbaar te wees vir beoordelingsfoute is daar die afgelope paar jaar aandag geskenk aan die ontwikkeling van gedragsgeoriënteerde beoordelingsmetodes. Dit word aangevoer dat laasgenoemde minder onderworpe is aan beoordelingsfoute. Hierdie studie het die beoordelings van 'n groep werkers op 'n grafiese beoordelingskaal en 'n gedragswaarnemingskaal met mekaar vergelyk. Die resultate kon nie ondersteuning verleen aan die standpunt dat grafiese skale meer vatbaar is vir beoordelingsfoute nie.