RECOMBINANT DNA first forcefully caught the attention of the public and the press in July 1974 with the publication in Science of a letter from a committee of eminent molecular biologists appointed by the National Academy of Sciences (NAS). These scientists urged a moratorium on certain types of gene-splicing experiments, the moratorium to last until the biological hazards of recombinant DNA research could be assessed. The letter also recommended that the director of the National Institutes of Health (NIH) develop a set of safety procedures for working with recombinant DNA molecules.  A world-wide voluntary moratorium by molecular biologists then began and lasted more than two years.