Sarcopenia, skeletal muscle loss during aging, is associated with increased falls, fractures, morbidity, and loss of independence. MicroRNAs (miRNA) are novel post-transcriptional regulators. It is unknown what role miRNAs play in cell size regulation after an anabolic stimulus in human skeletal muscle. We hypothesized that aging would be associated with a differential expression of skeletal muscle primary (pri) and mature miRNAs (miR). To test this hypothesis, the expression of muscle-specific miRNAs (miR-1, -133a, -206), upstream regulators (myoD, myogenin), and downstream targets (IGF1, HDAC4, MEF2, Rheb) in skeletal muscle of young and old men were measured using real-time PCR and immunoblotting before and after an anabolic stimulus (resistance exercise + ingestion of a 20g leucine-enriched essential amino acid solution). Muscle biopsies were obtained at baseline, and 3 and 6h post-exercise. At baseline, we found pri-miRNA-1-1, -1-2, -133a-1, and -133a-2 expression elevated in old compared to young (P<0.05). Pri-miRNA-1-2, -133a-1, and -133a-2 were reduced at 6h post-exercise only in the young compared to baseline whereas levels of pri-miRNA-206 were elevated at different post-exercise time points in old and young (P<0.05). As compared to baseline, miR-1 was reduced only in the young while Rheb protein increased in both age groups following the anabolic stimulus (P<0.05). We conclude that skeletal muscle primary and mature miRNAs expression in young men is readily altered by an anabolic stimulus of resistance exercise + essential amino acid ingestion. However, aging is associated with higher basal skeletal muscle pri-miRNA expression and a dysregulated miRNA response following the anabolic stimulus.