This research was undertaken to study the efficiency of methods of osmotic conditioning of lettuce seeds on the germination. Seeds from two lots
of lettuce cultivar Repolhuda Brasil 303 were submitted to osmotic conditioning in solutions of Mannitol 035 Molar and Polyethylene Glycol 25% for periods of 4 and 7 days, under constant temperature (20oC) and light. The seeds were surface dried for 2 hours at room temperature, air dried for 48 hours at room temperature or oven dried with air flow for 12 hours at 32oC. The evaluations were done at two month intervals during ten months storage, consisted of a germination test, first count of the germination test and germination with prechill. The results indicated that osmotic conditioning of lettuce seeds in the solution of Mannitol 0.35 Molar for a four days period at 20oC, improves the performance of low physiological quality seed lots.