Freshly harvested tomato (Lycopersicon esculentum Mill, cv. Moneymaker) seeds were osmotically primed for 8 d in −1.0 MPa PEG-6000 solution and dried to about 6% water content for storage. Such so–called ‘fresh PEG priming’ enhanced seed germination and improved seedling performance as compared with the untreated control. Fresh PEG priming neither alleviated seed dormancy nor promoted DNA replication as was the case when seeds were dried upon harvest and subsequently primed in PEG (normal PEG priming). However, the addition of 10 μM GA4+7 to the osmotic priming solution triggered replicative DNA synthesis of fresh-priming seeds and further enhanced the germination process. After 5 months of storage in ambient temperature conditions, fresh PEG-primed seeds maintained more positive effects gained from priming, whereas, normal PEG-primed seeds had lost the promoting effects on germination. Normal PEG-primed seeds were much more susceptible to controlled deterioration than fresh PEG-primed seeds. It is suggested that the advancement of germination is negatively correlated with seed storability. The mechanisms of seed priming in relation to nuclear replication activities and physical changes are discussed.