The effects of three levels of plant density (10, 14 and 28 plants/m²) and four GA₃ concentrations (0, 5, 10 and 15 p.p.m.) on Romaine c.v. were studied during the growing seasons of 1994 and 1995. The results indicated that the flowering stem height, percentage of mature inflorescence, no. of flower head inflorescence, percentage of heavy seed and seed yield/m² reflected significant and successive increments as a result of increasing the plant density. However, the no. of inflorescences / plant, flower heads quality, percentage of light seed and seed yield/plant, reflected reversal trends. The plant density had no effect on seed weight/flower head, seed index and germination percentage. Spraying lettuce plants with GA₃, up to 10 p.p.m. increased successively the percentage of mature inflorescences, no. of inflorescences/plant, no. of flower heads/inflorescence, flower head quality, percentage of heavy seed and total seed yield per plant and per square meter. The seed index values and germination percentage of produced seeds were not effected by GA₃ concentration. The best treatment combination for the production of high seed yield and quality was found to be that of sowing lettuce plants at the highest plant density (28 plants/m²) and spraying the growing plants with 10 p.p.m of GA₃.