The Middle European Mathematical Olympiad (MEMO) is the continuation of Austrian-Polish Mathematical Competition (APMC), held 29 times from 1978 to 2006. Now ten countries participate in the MEMO: Austria, Croatia, Czech Republic, Germany, Hungary, Lithuania, Poland, Slovakia, Slovenia and Switzerland. The 5th Middle European Mathematical Olympiad was held in Varaždin, Croatia, from 1st to 7th September 2011. About a hundred participants came, including 60 contestants and 20 team leaders and their deputies. On the photo prof.dr. Ilko Brnetić, University of Zagreb, chairman of the Jury.