On 15 June 1999 our colleague and friend Leo van Rossum died of the consequences of a heart attack. Leo had – often unbeknownst to readers – played a major role in the development of the International Review of Social History. As a member of the Editorial Board for over three decades (from 1964 to 1995), he enhanced the journal's quality immeasurably through his stimulating suggestions and meticulous critiques of texts.

As a staff member of Amsterdam's International Institute of Social History (which issues the Review), Leo van Rossum ran the east-European activities for many years. He collected archives, arranged scholarly publications and advised countless researchers who approached him. His impressive command of languages (in addition to Dutch, French, German, English, and Spanish, he knew Russian, Polish, Serbo-Croat, Czech, Romanian, and Bulgarian), his vast knowledge of east-European social history, and his considerable charm repeatedly left a deep impression.

The rescue of east-European archives may have been Leo's greatest achievement. Over time he preserved many documents that might otherwise have been lost, especially of left-wing opposition movements and persons. After the changes of 1989–1990 Leo was deeply involved in the fate of archives in danger of being neglected.