The complete S-RNA sequences of four Bulgarian and one German isolate of tomato spotted wilt tospovirus were determined. All isolates show a high conservation in their N proteins, while the NSs proteins and the intergenic regions (IGR) are more variable. The Bulgarian isolate 10HK96 has the largest S-RNA (3364 nucleotides) among tomato spotted wilt viruses reported so far. The enlargement is based on an insertion of 365 nts in the IGR that may have resulted from stuttering of the viral polymerase or non-homologous recombination. This insertion is present in the N protein gene subgenomic messenger, upstream of a proposed transcription termination signal.