Expanded interest in studying the mechanisms of elongation and termination during transcription has come as a result of several recent findings that highlight the importance of the regulation of these processes in human health. Several cellular proto-oncogenes contain regulated blocks to elongation (1), and the human immunodeficiency viruses also control gene expression in part by regulating the efficiency of elongation in response to the trans-activating protein, TAT (2). This review considers these recent findings and compares potential mechanisms of regulation used by prokaryotic and eukaryotic RNA polymerases during elongation and termination. In all these systems, many of the detailed mechanisms of transcription elongation and termination are still to be defined; however, we have tried to group examples that may share some common regulatory elements into simplified categories.