The current debate on the ethics of stem-cell research (see above) was launched by the work of James Thomson, who isolated human embryonic stem cells from the inner cell mass of embryos left over at fertility clinics. Thomson relied on private money from Geron, a Californian biotechnology company, to achieve his feat. Private work with stem cells is legal in the United States, and is likely to remain so. The debate centres on whether such work should receive federal funding.

But Thomson, a developmental biologist at the University of Wisconsin-Madison, says his private-sector financing has left him far from untouched by the ban on federal funding.

This is because the ban requires strict separation of stem-cell work from federally funded work. Thomson had to set up a physically separate laboratory in 1997 when he launched his effort to isolate the cells.

That laboratory, at the Clinical Science Center at the University of Wisconsin Hospital and Clinics in Madison, is not as well equipped as his main laboratory. Thomson has been forced to limit his current research to basic tissue-culture manipulation experiments. Tantalizing challenges, such as identifying the genes that direct stem cells to become one tissue type or another, are being deferred through lack of equipment.

Thomson is therefore anxiously awaiting the publication of the NIH guidelines that will tell investigators how to proceed when applying for, and using, federal funding for the research. Despite the Congressional ban, the biomedical agency thinks it is permitted to fund research on stem cells, following advice from lawyers in the Department of Health and Human Services. The publication of guidelines will signal that the NIH is ready to begin issuing grants.