GAMSAT scores can be used for two consecutive years. This means that candidates may apply for admission to the graduate-entry schools up to two years after the date on which they sit the test. For example, results from GAMSAT Australia 2013 will be valid for application to a graduate-entry medical, dental, pharmacy or optometry program commencing in 2014 and/or 2015, but not in 2016.
If you have two valid GAMSAT scores, you may use whichever you prefer in applying for admission to medical or dental school, pharmacy or optometry. The University Admissions Committees will not have access to your GAMSAT scores from other years.
In making your decision you should bear in mind that the Admissions Committees may set thresholds for the Section scores as well as for Overall Scores. If you are uncertain which result to use on your application, you should check the websites of your preferred schools for guidance.
There is no restriction on the number of times a bona fide candidate may sit GAMSAT.