This chapter explains the types of RNA genome analyses to be considered, the methods available to carry them out, and the results of nucleotide sequencing. It proposes a population equilibrium model for RNA genomes and discusses its implications. The results of S. Spiegelman's group represented the first amplification of an infectious genome in the test tube and paved the way for numerous interesting experiments on evolution of self-replicating RNA molecules in vitro. The chapter reviews early evidence of genetic variability of rhabdoviruses and discusses the several direct sequencing or indirect phenotypic methods for the analysis of RNA Genome populations. Direct methods comparison of RNAs, either by sampling of nucleotide sequences for example oligonucleotide fingerprinting or by determination of nucleotide sequences for example RNA or cDNA sequencing or cDNA synthesis and molecular cloning and sequencing. Indirect methods, some measurable phenotype are used to infer a genetic difference at the locus encoding a protein involved in that phenotype.