Sir

Japan's Institute of Physical and Chemical Research, RIKEN, has now published its investigation into US accusations of espionage against Takashi Okamoto, head of the institute's laboratory for neurodegeneration signalling (see Nature 411, 225; 2001 and Nature 411, 991; 2001).

RIKEN's report, whose main author is chief executive Shun-ichi Kobayashi, concludes that there is no evidence that the institute intentionally planned to bring in the materials from the United States. But Okamoto has remained silent on the issue, and has now abruptly left RIKEN.

This affair has shocked Japanese scientists and highlights the differences in definitions of 'originality' between Japan and the United States. The United States encourages excellent scientists from all over the world to work there on short-term contracts, and is understandably keen to maintain its competitive edge. But to avoid similar misunderstandings in future, the US government should issue clear guidelines for foreign researchers about originality and authorization for removal of research materials.