The National Hemophilia Foundation supports gene therapy as the most promising strategy for curing hemophilia. At this time, NHF also supports the position advocated in the Orkin-Motulsky report on gene therapy that gene therapy should be somatic only, i.e. there should be no attempt to alter the germline cells. In assessing potential for inadvertent germline transmission, NHF agrees with an approach that classifies protocols into one of three groups based on pre-clinical studies, i.e. absence of vector sequences in gonads, transient positivity, or persistent positivity in the gonads, with recommendations for appropriate subjects for inclusion in a trial to be made on that basis. NHF believes that this risk, like other potential risks, should be weighed against the potential benefits to be realized from successful gene therapy for hemophilia. We urge the Recombinant DNA Advisory Committee (RAC) of the National Institutes of Health to allow protocols to proceed with appropriate monitoring and safeguards.