Genome-encoded regulatory small RNAs are classified into 3 groups; microRNAs (miRNAs), endogeneous small interfering RNAs (endo siRNAs) and piwi interacting RNAs (piRNAs). miRNAs, 17-21 nucleotide in size, are involved in posttranscriptional gene regulation via precise or imprecise base pairing with target mRNAs resulting in either target mRNA degradation or translational inhibition. Endo siRNAs ,on the other hand, may function transposon regulation but their precise regulatory function and mechanism have not been elucidated yet. piRNAs are mainly involved in transposon silencing in spermatogenesis. Despite their discovery, biological roles and modes of functions of small RNAs remain to be elucidated. The aim of this thesis was to identify polysome-associated small RNAs in Drosophila melanogaster embryos by deep sequencing and investigate their role in translational regulation. Deep sequencing and microarray results determined stage and fraction specific distribution of genome encoded small RNAs. Surprisingly, the results implied that mRNAs may be posttranscriptionally regulated by antisense transcripts in polysome.