ACCORDING to Kirsten et al.1 and Hintenborger2, the frequency distribution curves of the potassium-argon ages of stone meteorites show two distinct maxima. One occurs at ages close to 4.5 × 109 years, the other occurs around 1 × 109 years. However, if one classifies the chondrites into the Urey-Craig3 L- and H-groups a relationship between classifications and gas retention ages is apparent (Fig. 1). The classification in L- and H-groups (that is, hypersthene-olivine and bronzite-olivine chondrites respectively) is based on the following chemicalmineralogical parameters: bulk iron3, specific gravity4, metallic nickel-iron4,5, and Fe/Fe + Mg ratios in olivine and rhombic pyroxene6,7. Only well-classified chondrites have been included. Carbonaceous chondrites and enstatite chondrites have been excluded since they constitute separate groups7. Fig. 1 shows the frequency distribution of chondrites with well-known classification and well-determined age. The age values were taken from Anders8 and Kirsten et al.1. The diagram shows that the substantial degassing, which leads to an apparent potassium-argon age of about 1 × 109 years, is, on the basis of the chondrites investigated so far, considerably more frequent for the L-group of chondrites than for the H-group. The uranium-helium ages are also plotted in the diagram, showing a similar effect. New potassium-argon age measurements9 seem to yield some more H-group chondrites with low potassium-argon ages. However, recent uranium-helium measurements10 again seem to support an age-classification relationship as indicated in Fig. 1. The purpose of this communication is to direct attention to the apparently more frequent, substantial degassing of L-group chondrites in comparison to H-group chondrites, and to emphasize the necessity for more potassium-argon gas retention age measurements of chondrites, for which the classification into L- and H-groups is well known.