Dr. Collins said the N.I.H. would set up a working group to decide how to carry out the recommendations. Until the group finishes its deliberations, no new grants would be awarded and all N.I.H. chimpanzees that are not already enrolled in experiments would not be involved in any further research projects. Dr. Collins did not offer a timeline or say how many chimpanzees were currently involved in research.

Use of chimpanzees has already been waning, partly because it is expensive. The report covers only chimps owned or supported by the government, 612 of a total of 937 chimps available for research in the United States. Only a few are in experiments at any one time.

The committee identified two areas where it said the use of chimpanzees could be necessary. One is research on a preventive vaccine for hepatitis C. The committee could not agree on whether this research fit the criteria and so left that decision open.

In the second area, research on immunology involving monoclonal antibodies, the committee concluded that experimenting on chimps was not necessary because of new technology, but because the new technology was not widespread, projects now under way should be allowed to reach completion.

The report offered two sets of criteria, one for biomedical experiments, which it said could be considered necessary when there was no other way to do the research — with other animals, lab techniques or human subjects — and if not doing the research would “significantly slow or prevent important advancements to prevent, control and/or treat life-threatening or debilitating conditions.”

For behavioral and genomic experiments, the report recommended that the research should be done on chimps only if the animals are cooperative, and in a way that minimizes pain and distress. It also said that the studies should “provide otherwise unattainable insight into comparative genomics, normal and abnormal behavior, mental health, emotion or cognition.”