Abstract: Although the programmed retention index is not theoretically justified, as the Kováts index system, it is of more general use. It could serve as additional parameter for a more precise identification of organic compounds during GC/MS analyses. So, one gains to define it precisely. A method has been described for the calculation of linear programmed retention indices based on Bezier curves smoothing, which shows some advantages in comparison with the Van den Dool and Kratz`s method. For the mathematical procedure the standards do not necessary have to belong to a homologous series.