The successes of recombinant-DNA technology paradoxically may be thwarting many of its principal advocates, particularly those who would like to learn how genes in complex organisms are controlled. After the heady bursts of progress during the past few years, scientific efforts in gene-splicing have plateaued, say several scientists who attended the third annual Congress for Recombinant DNA Research, held early this month in Philadelphia. This is not to deny the many successes being marked. However, although those successes often have been won against increasingly more challenging problems, they also have tended to recapitulate earlier efforts. The net effect is that this field is moving horizontally but not vertically, with scientists successfully isolating (or cloning) more and more difficult genes but not changing a fundamental understanding of them. Research in several labs on metallothionein genes gives an idea how frustrating partial successes can be, and how they also serve to distract scientists f...