A common modification of eukaryotic and bacterial tRNAs is isopentenylation of the adenosine at position 37, with the formation of isopentenyladenosine. N6-Isopentenyladenosine plays a major role in posttranscriptional processes, including the function of mammalian selenocysteine tRNA. This molecule seems to have metabolic effects that, for its relationships with isoprenoid metabolism and its direct biological activities, affects mammalian cell cytoskeleton, proliferation and apoptosis. In addition, preliminary clinical observation seems to indicate a possible use of N6-Isopentenyladenosine as anticancer drug.