The viability of watermelon seeds kept under different storage conditions, was studied during a period of 18 months. The experimental results presented in this paper drew the following conclusions: 1) Complete viability at the end of 18 months was obtained for seeds stored at 20°C and at relative humidity of 45%. 2) At this same temperature, the longevity of the seeds decreased with the increasing of relative humidity. 3) Seeds kept at 30°C, even in low relative humidity condition, lost their viability in a short time. 4) The seeds of watermelon stored in airtight containers at room temperature, kept their viability well for 12 months, after which time it decreased considerably.