River Danube is the second biggest European river flowing through 10 European countries thus, in a sense, unifying them.
Also, science unifies countries, and organic chemistry is an example of this declaration. After the fall of the „Iron curtain, “ Professor Sauter (Technische Universitat Wien) visited Slovakia Bratislava to form a closer scientific link between the two closest lying capitals in Europe (of course, Vatican City and Rome). One of the results of these talks about cooperation has been an invitation to start mutual seminars in organic chemistry called “Blue Danube Symposia on Heterocyclic Chemistry” organised in Austria. Next year this event was organized in Slovakia and after that Hungary (prof. Hajós), the Czech Republic (prof. Potáček) and Slovenia (prof. Stanovnik) joined this activity:
| 1 BDSHC | 24.-25.9.1991 | Vienna | Austria |
| 2 BDSHC | 13.-15.4.1992 | Smolenice | Czechoslovakia |
| 3 BDSHC | 25.-28.4.1993 | Sopron | Hungary |
| 4 BDSHC | 22.-25.4.1994 | St. Pölten | Austria |
| 5 BDSHC | 14.-17.6.1995 | Častá-Papiernička | Slovakia |
| 6 BDSHC | 1.-4.9.1996 | Brno | Czech Republic |
| 7 BDSHC | 7.-10.6.1998 | Eger | Hungary |
| 8 BDSHC | 24.-27.9.2000 | Bled | Slovenia |
| 9 BDSHC | 16.-20.6.2002 | Tatranská Lomnica | Slovakia |
| 10 BDSHC | 3.-6.9.2003 | Vienna | Austria |
| 11 BDSHC | 28.8.-1.9.2005 | Brno | Czech Republic |
| 12 BDSHC | 10.-13.6.2007 | Tihany | Hungary |
| 13 BDSHC | 20.-23.9.2009 | Bled | Slovenia |
| 14 BDSHC | 26.-29.6.2011 | Podbanské | Slovakia |
| 15 BDSHC | 1.-5.9.2013 | Olomouc | Czech Republic |
| 16 BDSHC | 14.-17.6.2015 | Balatonalmádi | Hungary |
| 17 BDSHC | 30.8.-2.9.2017 | Linz | Austria |
| 18 BDSHC | 19.9.-21.9.2019 | Ljubljana | Slovenia |
| 19 BDSHC | 22.8.-24.8.2022 | Bratislava | Slovakia |