Argumentation systems aim to reflect how conflicting information is 
used in cognition to construct and analyse arguments. So these 
systems involve identifying arguments and counterarguments relevant 
to an issue (e.g. What are the pros and cons for the safety of 
mobile phones for children?). They may also involve weighing, 
comparing, or evaluating arguments (e.g. What sense can we 
make of the arguments concerning mobile phones for children?) 
and they may involve drawing conclusions (e.g. A parent answering 
the question ``Are mobile phones safe for my children?"). In addition, 
they may involve convincing an audience (e.g. A politician making the 
case that mobile phones should be banned for children because the 
risk of radiation damage is too great).  In this talk, I cover some of 
the basics of the theory and implementation of logic-based 
argumentation systems and then cover some work we are doing on 
an application in analysing evidence from clinical drug trials on 
treatments for breast cancer.