The public expects that the services provided by professionals, such as physicians or accountants are reliable. As the public becomes more concerned about visual impacts, it is to be expected that questions will be raised about the reliability of visual impact assessment methods. This paper presents a case study investigating three types of reliability: rater reliability, test-retest reliability, and firm reliability. Reliability is generally found to be good but may not reach the highest professional standard. The comparison of two firms suggests there may be a subtle client bias.