Twelve true potato seed (TPS) crosses were tested for seedling vigor after 3 and 6 months of storage. Bulk seed was sown in the 3-month test, and high- and medium-density seed was sown in the 6-month test. Treatments consisted of pre-sowing in solutions of KNO3 + K3PO4 at -10 MPa for 5 days (priming), and in gibberellic acid at 1500 ppm (GA) or in water for 1 day; rinsed seed served as a control. In both the 3- and 6-month tests, seedlings of Atlantic x LT-7 (A1) outperformed all other crosses in rate of emergence and dry weight. Overall performance increased for all crosses when tested after 6 months of storage. In the 3-month test, the priming treatment increased seedling vigor in cross A1, otherwise, differences among treatments were mostly not significant. In the 6-month test, however, priming increased vigor in all crosses. Emergence generally was >80% in both tests. After 3 months, however, GA increased the percentage of emergence from ≤38% to 73% in the two least vigorous or most dormant crosses. Seed density levels were neither strongly nor consistently related to seedling vigor. The findings suggest that considerable improvement of TPS seedling performance can be attained by 1) selecting more vigorous or less dormant TPS progenies; 2) sowing seed after 6 months in storage; and (3) priming seed. © 1990 Springer.