C.elegans Argonaute-small-RNA pathways function in epigenetic inheritance.For example, the PIWI Argonaute PRG-1 initiates RNA-induced epigenetic silencing (RNAe), in which silent alleles send trans-silencing signals.Here we describe RNAinduced gene activation, which we term RNAa, in which active alleles send trans activating signals.RNAa requires the CSR-1 Argonaute both maternally and paternally.CSR-1 engages antisense small RNAs targeting nearly all germline-expressed mRNAs.The acquisition of RNAa status by a transgene correlates with accumulation of complementary antisense CSR-1-associated small RNAs.These findings suggest that Argonaute-small-RNA complexes function as trans-generational binary signals that program gene expression from one generation to the next.