Abstract: There is disclosed a method of quantitating nucleic acids in a sample by using nucleic acid amplification, wherein, prior to the amplification step, a given amount of a known nucleic acid molecule is added to the sample as internal standard, which standard nucleic acid molecule differs from the nucleic acid to be quantitated by at least one detectable characteristic; to obtain a high precision and good reproducibility, known amounts of at least two known nucleic acid molecules which differ from each other and from the nucleic acid to be quantitated in at least one detectable characteristic are added as an internal standard to the sample prior to nucleic acid amplification, the amounts of amplified sample and standard nucleic acids obtained are determined, and from the amounts obtained, the amount of the nucleic acid to be quantitated originally present in the sample is determined.