This is the fifth time a "Horticultural Research International" has been published, again revised and extended. Since 1986 a lot has changed in the world: new countries with old names appeared on the map, while recognized frontiers vanished. As the organizing editors we tried to follow these evolutions as closely as possible. In many cases we were able to establish communication with our correspondents as usual; nevertheless we had to delete a total of 8 countries. Thanks to correspondents from 74 different countries we are now able to present this edition, comprising a total of 1800 institutes, including 20,000 names of individual research workers. We are very grateful to the correspondents from 17 newly enlisted countries who performed pioneer work for us. Noteworthy is the fact that especially the Asian continent made a leap forward with contributions from 13 countries in 1986 to 19 in the present volume of "Horticultural Research International". At the secretariat we will continue to extend our network, so please feel free to send us any suggestions or additions you would like to make. For the first time we added a list of international organizations relevant to horticulture. In the editing process a further standardization has been used to reach an easily readable and comparable survey per country. Hopefully this directory will again facilitate cooperation on a worldwide scale among horticulturists active in governmental, academic, extensional, educational, technical or commercial fields.