In the past few months, animal-rights groups have stepped up their demonstrations against academic researchers who use animals, spawning a new wave of concern among scientists. In February, extremists caused a fire at the home of a researcher from the University of California at Los Angeles, and protesters struck the husband of a scientist from the University of California at Santa Cruz. Scientific leaders fear the attacks are having a chilling effect on American biomedical research and are driving scientists out of the field. Yet "The Chronicle"'s own analysis of federal grants and numerous interviews with scientists suggest that researchers are not abandoning animal experimentation. Even researchers who have been the targets of attacks and protests have generally continued with their work. The recent activism has, however, cowed many scientists into silence. With few researchers willing to explain the importance of their work, public support for the use of animals in research will dry up, warn science advocates. Other organizations are trying to counter the message that animal-rights groups are sending by setting up pro-research groups, speaking out and opening up their labs.