A new male-sterile tomato mutant characterized by morphologically normal flowers and acetocarmine-stainable mature pollens, was induced by irradiating seeds with gamma rays. Mature pollen grains which stain black by iodine solution at anthesis, exhibited a lower germination rate and proved to be self-unfruitful by self-pollination in spring. Thus, the inhibition of starch degradation is associated with the low pollen germination, but whether it causes pollen sterility is unclear. From the segregation ratio of self-pollinated progenies of heterozygous plant (Msms), both inhibition of starch degradation and male sterility were controlled by single recessive genes, respectively, which might be activated at the post maturation stage of pollen.