This investigation is aimed at providing detailed information to aid in our understanding the phenomenon of RNA processing and how these processes are involved in the post-transcriptional regulation of gene expression in a biological system. We are using the bacteriophage lambda which infects Escherichia coli as the model system for study because it is extremely amenable to the refined biological and biochemical techniques presently available for the detailed analysis. Our principal objectives are: (1) to define the specific RNA processing and decay events with respect to their location on the bacteriophage RNA transcripts and to identify the enzymatic activities involved in these events. (2) to establish the role of these RNA processing and decay events in the post-transcriptional regulation of specific bacteriophage proteins and how these processes affect development of the bacteriophage. These phenomena are prominent in eukaryotic cells but are very difficult to analyze at the detailed levels feasible in the bacteriophage lambda system.