The light noble gases He, Ne and Ar have been measured in the iron meteorites Dongling, Nantan andNingbo. Dongling and Ningbo show a deficit of cosmic-ray that produced ~3He of ca. 30% and 10%,respectively, which is argued to be caused by the loss of ~3H (tritium) from the meteoroids during the time oftheir exposure to the cosmic radiation. Nantan has the lowest eontent of noble gases as yet reportcd for anyiron meteorite. Cosmogenic ~3He and ~(38)Ar are only about 1/5000 of those in Dongling which has particularlyinteresting implications if the two meteorites belong to the same fall. In addition, Nantan contains non-spallogenic ~4He which we believe to be of radiogenic origin. This radiogenic~4He, together with a U-content of2.6×10~(-11)g/g yields a ~4He retention age close to the cosmic-ray exposure age of Dongling. If Donglingand Nantan were part of the same meteoroid, this result would indicate that He retention in the meteoroidstarted only at or after onset of the exposure to the cosmic radiation. On the other hand, if the He retentionage were 4,500 Ma, a U-content of less than 7.2×10~(-13)g/g is required to explain the non-cosmogenic _4Hepresent. An upper limit to the number of transuranium or superheavy-element atoms which have deeayed byx-emission in Nantan since onset of He retention is 2×10~(10) per gram. The light noble gases He, Ne and Ar have been measured in the iron meteorites Dongling, Nantan andNingbo. Dongling and Ningbo show a deficit of cosmic-ray that produced ~ 3He of ca. 30% and 10% respectively, which is argued to be caused by the loss of ~ 3H (tritium) from the meteoroids during the time of their exposure to the cosmic radiation. Nantan has the lowest eontent of noble gases as yet reportcd for anyiron meteorite. Cosmogenic ~ 3He and ~ (38) Ar are only about 1/5000 of those in Dongling which has particularlyinteresting implications if the two meteorites belong to the same fall. In addition, Nantan contains non-spallogenic ~ 4He which we believe to be of radiogenic origin. This radiogenic ~ 4He, together with a U -content of 2.6 × 10 ~ (-11) g / g yields a ~ 4He retention age close to the cosmic-ray exposure age of Dongling. If Donglingand Nantan were part of the same meteoroid, this result would indicate that He retention in the meteoroidstarted only at or after onset of the exposure to the cosmic radiation. On the other hand, if the He retention capacity were 4,500 Ma, a U-content of less than 7.2 × 10 ~ (-13) g / g is required to explain the non-cosmogenic _4Hepresent. An upper limit to the number of transuranium or superheavy-element atoms which have deeayed byx-emission in Nantan since onset of He retention is 2 × 10 ~ 10 per gram.