We exploited mutants that become progressively sterile to study telomerase-mediated telomere repeat addition, deficiency for which in humans results in transgenerational telomere erosion accompanied by lethal diseases anemia or pulmonary fibrosis. Moreover, telomere erosion may be broadly relevant to human cellular aging because telomerase is silenced in human somatic cells. We recently identified a novel class of small RNAs composed of (TTAGGC)n telomere repeats that are exceptionally rare in mammals and C. elegans but are abundant in the closely related nematodes, C. briggsae and C. remanei. This indicates a dramatic change in telomeric small RNA biogenesis in recent evolution. We discovered that small RNA-mediated genome silencing promotes telomere stability in the absence of telomerase, and we are interested in broadly understanding the biogenesis and function of telomeric small RNAs.