Fission-produced -emitting radionuclidic impurities in eluates obtained by elution of routine (n,f)99Mo/99mTc generators have been determined. Four radionuclidic impurities were identified and quantitatively measured by the method of -spectrometry. The distribution of103Ru,106Ru,125Sb and131I in the eluates was followed. The fraction of the activity which has been desorbed from alumina in the generator column during the lifetime of the generator was determined for earch radionuclide found. The contents of radionuclidic impurities in the eluates were compared with the criteria of radionuclidic purity prescribed by the Pharmacopoeia.