This investigation was caarried out at Shandaweel Experimental Station, Sohag Governorate in 1989/90, 1990/91 and 1991/92 sea‌sons to study the effect of Two transplanting dates and three planting densities (80, 120 and 160 plants/m2) on bulb yield and quality of on‌ion variety Giza 20. Results were as follows : 1.Highest marketable and exportable bulb yields were produced by transplanting 160 plant/m2 in November 15. 2.Percentages of external doubling and bolting were significantly de‌creased by planting on February 5. 3.Percentages of external doubling was significanting 80 plants/m2 on February 5. 5.Average bulb weight was significantly decreased by transplanting 160 pIants/m2 on February 5. 6.Plants matured on April 17 and 27 for Nov. 15 and Feb. 5 transplant‌ing dates. 7.Bulb weight was greatly reduced in late transplanting date (Feb.5).