Number of eligible participants per centre in the European Community Respiratory Health Survey (ECRHS) II as defined by number of responders to stage 2 of ECRHS I
| Country | Centre | Eligible participants from random sample | Eligible participants from symptomatic sample | Total eligible participants |
| Iceland | Reykjavik | 564 | 84 | 648 |
| Sweden | Umea | 552 | 156 | 708 |
| Uppsala | 622 | 201 | 823 | |
| Goteborg | 682 | 184 | 866 | |
| Estonia | Tartu | 431 | 127 | 558 |
| Norway | Bergen* | 835 | 0 | 835 |
| UK | Norwich | 473 | 108 | 581 |
| Ipswich | 448 | 111 | 559 | |
| Germany | Hamburg*,# | 1252 | 0 | 1252 |
| Erfurt* | 731 | 0 | 731 | |
| The Netherlands | Groningen*,¶ | 380 | 0 | 380 |
| Geleen* | 415 | 0 | 415 | |
| Bergen-op-zoom*,¶ | 452 | 0 | 452 | |
| Belgium | Antwerp City | 564 | 87 | 651 |
| South Antwerp | 558 | 76 | 634 | |
| Switzerland | Basel | 853 | 149 | 1002 |
| France | Paris* | 652 | 0 | 652 |
| Bordeaux*,# | 544 | 0 | 544 | |
| Grenoble | 473 | 49 | 522 | |
| Montpellier*,# | 456 | 0 | 456 | |
| Spain | Oviedo | 357 | 167 | 524 |
| Galdakao | 486 | 106 | 592 | |
| Barcelona | 393 | 123 | 516 | |
| Albacete | 435 | 191 | 626 | |
| Huelva | 271 | 132 | 403 | |
| Italy | Verona | 340 | 18 | 358 |
| Pavia* | 310 | 0 | 310 | |
| Turin | 244 | 111 | 355 | |
| USA | Portland# | 723 | 116 | 839 |
| Australia | Melbourne# | 669 | 207 | 876 |
| Total | 16165 | 2503 | 18668 |
*: centres who, due to limited resources, only studied a representative sample of responders to stage 1 and therefore have no “symptomatic sample”
#: non-European Union funded centres taking part at their own expense
¶: at the time of writing this paper it was unlikely that this centre would provide data for ECRHS II