On Monday, July 11, 2011 the fourth Measurement Science in Chemistry International Summer School started in a west-central city of Poland in Poznań. There are students from fourteen countries. The summer school covers a wide-ranging list of topics: Importance of reliable measurements to implement EU legislation, Basic aspects of uncertainty, Validation of chemical analysis, Traceability in chemical analysis procedures, ISO 17025, On the use of Certified Reference Materials, Ecology Station in Jeziory: sampling, Alternative Approaches for the Quantification of Measurement Uncertainty, Visit to accredited lab (Wodociągi Poznań), Basic statistics, practical examples. Special emphasis is put on group works and learning by role play.