Contamination from 131I, 103Ru, and 239Np in the eluate of 99Mo-99mTc generators loaded with (n, gamma)-produced 99Mo. 
Iodine-131, ruthenium-103, and neptunium-239 are present as contaminants in the eluate of 99Mo-99mTc generators loaded with 99Mo prepared by thermal-neutron irradiation of enriched 98Mo.  The elution pattern of each of these contaminants is determined, together with the amounts found in the eluate of all generators tested over a 7-month period.