Sequencing and computer analysis of the nucleotide sequence of variola major virus strain India-1967 (VAR-IND) DNA segment (23 786 bp) covering the left variable region of the viral genome has been carried out. Twenty-nine potential open reading frames were identified. Structure-function organization of the VAR-IND DNA segment was compared with previously reported sequences from analogous genome regions of vaccinia virus strains Copenhagen (VAC-COP) and Western Reserve (VAC-WR). Multiple structural differences between the VAR-IND and genome regions were analysed and both VAC-COP and VAC-WR have been found. Possible molecular factors of virulence, virus host range genes as well as differences revealed in the structure of these genes of VAR and VAC will be discussed.