Treatment of the RNA of satellite tobacco necrosis virus (STNV) with phosphomonoesterase followed by heat denaturation and treatment with polynucleotide kinase in the presence of [gamma-32P]ATP yields a STNV [5'-32P]RNA containing a homogeneous 5' terminus. Analyses of this STNV [5'-32P]RNA yield the sequence of the first 42 nucleotides from the 5'terminus of STNV RNA. This nucleotide sequence contains the translation initiation AUG codon starting at position 30 from the 5' terminus as indicated by match of subsequent nucleotides with the genetic code assignments for the N-terminal amino acids of STNV coat protein in the 5'-terminal sequence ppAGUAAAGACAGGAAACUU-UACUGACUAACAUGGCAAAACAAC. An interesting feature of this sequence is its potential to form a hairpin loop structure involving perfect Watson-Crick base pairing between the first seven nucleotides and nucleotides at positions 16--22.