A Bonny Best (G1187) tomato plant had some white leaflets and some gray-green leaflets with white margins. Seeds from this plant produced nearly 100 seedlings all of which had yellow cotyledons that did not turn green, so the seedlings died. The symptom resembled that described for the radium-induced, lethal ys-allele. Similarly, seeds were saved from two branches with white or yellow areas in their leaflets on a Lakeland (Gl396) tomato plant the other branches of which were normally green. The resulting seedlings were yellow and died when they were about 1/2 inch tall. A third case behaved differently. An F2 plant of G1417 (Southland x L. e. cerasiforme) produced a yellog-leaf branch on one plant; its other branches looked normal. Seeds from this branch produced 75 seedlings with normal green leaves and 126 plants with yellow leaves (Gl573). The yellow-leaf plants all died without growing taller than 2 inches. The green-leaf seedlings were set in a field where all of them produced normal green plants. This yellow-leaf mutation apparently is due to a chromosome deficiency that makes impossible the production of chlorophyll. It occurred in 3 tomato plants that appeared to be normal except for 1 to 3 branches with albino leaves. Although a method of proof is unavailable, it is convenient to ascribe this kind of albino mutation to the ys-allele. Thus, the ys^+^-allele is expressed as normal ability to produce chlorophyll. The ys-allele or one similar to it appears occasionally as a recurrent mutation.